diff --git a/docstore/driver/driver.go b/docstore/driver/driver.go
index bd2bbccb0e..716012d650 100644
--- a/docstore/driver/driver.go
+++ b/docstore/driver/driver.go
@@ -219,7 +219,7 @@ type Query struct {
 // TODO(#1762): support comparison of other types.
 type Filter struct {
 	FieldPath []string    // the field path to filter
-	Op        string      // the operation, supports `=`, `>`, `>=`, `<`, `<=`, `in`, `not-in`
+	Op        string      // the operation, supports `=`, `>`, `>=`, `<`, `<=`, `in`, `not-in`, `array-contains`
 	Value     interface{} // the value to compare using the operation
 }
 
diff --git a/docstore/drivertest/drivertest.go b/docstore/drivertest/drivertest.go
index 404d33f056..83ed96e08b 100644
--- a/docstore/drivertest/drivertest.go
+++ b/docstore/drivertest/drivertest.go
@@ -1273,6 +1273,7 @@ type HighScore struct {
 	Score            int
 	Time             time.Time
 	WithGlitch       bool
+	GameCategories   []string
 	DocstoreRevision interface{}
 }
 
@@ -1316,15 +1317,21 @@ const (
 	game3 = "Days Gone"
 )
 
+var (
+	game1Category = []string{"Action", "Adventure"}
+	game2Category = []string{"Horror", "Comedy"}
+	game3Category = []string{"Action", "Adventure", "Horror"}
+)
+
 var highScores = []*HighScore{
-	{game1, "pat", 49, date(3, 13), false, nil},
-	{game1, "mel", 60, date(4, 10), false, nil},
-	{game1, "andy", 81, date(2, 1), false, nil},
-	{game1, "fran", 33, date(3, 19), false, nil},
-	{game2, "pat", 120, date(4, 1), true, nil},
-	{game2, "billie", 111, date(4, 10), false, nil},
-	{game2, "mel", 190, date(4, 18), true, nil},
-	{game2, "fran", 33, date(3, 20), false, nil},
+	{game1, "pat", 49, date(3, 13), game1Category, nil},
+	{game1, "mel", 60, date(4, 10), game1Category, nil},
+	{game1, "andy", 81, date(2, 1), game1Category, nil},
+	{game1, "fran", 33, date(3, 19), game1Category, nil},
+	{game2, "pat", 120, date(4, 1), game2Category, nil},
+	{game2, "billie", 111, date(4, 10), game2Category, nil},
+	{game2, "mel", 190, date(4, 18), game2Category, nil},
+	{game2, "fran", 33, date(3, 20), game2Category, nil},
 }
 
 func addHighScores(t *testing.T, coll *docstore.Collection) {
@@ -1491,6 +1498,11 @@ func testGetQuery(t *testing.T, _ Harness, coll *docstore.Collection) {
 			q:    coll.Query().Where("WithGlitch", "=", true),
 			want: func(h *HighScore) bool { return h.WithGlitch },
 		},
+		{
+			name: "GameCategories",
+			q:    coll.Query().Where("GameCategories", "array-contains", game1Category[0]),
+			want: func(h *HighScore) bool { return arrayContains(h.GameCategories, game1Category[0]) },
+		},
 		{
 			name:   "AllByPlayerAsc",
 			q:      coll.Query().OrderBy("Player", docstore.Ascending),
@@ -1529,13 +1541,14 @@ func testGetQuery(t *testing.T, _ Harness, coll *docstore.Collection) {
 				h.Score = 0
 				h.Time = time.Time{}
 				h.WithGlitch = false
+				h.GameCategories = nil
 				return true
 			},
 		},
 		{
 			name:   "AllWithScore",
 			q:      coll.Query(),
-			fields: []docstore.FieldPath{"Game", "Player", "Score", "WithGlitch", docstore.FieldPath(docstore.DefaultRevisionField)},
+			fields: []docstore.FieldPath{"Game", "Player", "Score", "WithGlitch", "GameCategories", docstore.FieldPath(docstore.DefaultRevisionField)},
 			want: func(h *HighScore) bool {
 				h.Time = time.Time{}
 				return true
@@ -2125,7 +2138,7 @@ func testAs(t *testing.T, coll *docstore.Collection, st AsTest) {
 	}
 
 	// ErrorCheck
-	doc := &HighScore{game3, "steph", 24, date(4, 25), false, nil}
+	doc := &HighScore{game3, "steph", 24, date(4, 25), game3Category, nil}
 	if err := coll.Create(ctx, doc); err != nil {
 		t.Fatal(err)
 	}
@@ -2164,3 +2177,12 @@ func checkCode(t *testing.T, err error, code gcerrors.ErrorCode) {
 		t.Errorf("got %v, want %s", err, code)
 	}
 }
+
+func arrayContains[T comparable](a []T, x T) bool {
+	for _, e := range a {
+		if e == x {
+			return true
+		}
+	}
+	return false
+}
diff --git a/docstore/gcpfirestore/query.go b/docstore/gcpfirestore/query.go
index ea714c134e..bd63525da5 100644
--- a/docstore/gcpfirestore/query.go
+++ b/docstore/gcpfirestore/query.go
@@ -274,7 +274,7 @@ func splitFilters(fs []driver.Filter) (sendToFirestore, evaluateLocally []driver
 	// Enforce that only one field can have an inequality.
 	var rangeFP []string
 	for _, f := range fs {
-		if f.Op == driver.EqualOp {
+		if f.Op == driver.EqualOp || f.Op == "array-contains" {
 			sendToFirestore = append(sendToFirestore, f)
 		} else {
 			if rangeFP == nil || driver.FieldPathsEqual(rangeFP, f.FieldPath) {
@@ -366,9 +366,8 @@ func newFieldFilter(fp []string, op string, val *pb.Value) (*pb.StructuredQuery_
 		fop = pb.StructuredQuery_FieldFilter_IN
 	case "not-in":
 		fop = pb.StructuredQuery_FieldFilter_NOT_IN
-	// TODO(jba): can we support array-contains portably?
-	// case "array-contains":
-	// 	fop = pb.StructuredQuery_FieldFilter_ARRAY_CONTAINS
+	case "array-contains":
+		fop = pb.StructuredQuery_FieldFilter_ARRAY_CONTAINS
 	default:
 		return nil, gcerr.Newf(gcerr.InvalidArgument, nil, "invalid operator: %q", op)
 	}
diff --git a/docstore/gcpfirestore/testdata/TestConformance/ActionsOnStructNoRev.replay b/docstore/gcpfirestore/testdata/TestConformance/ActionsOnStructNoRev.replay
index 2ac1e8087b..96cbebb733 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/ActionsOnStructNoRev.replay and b/docstore/gcpfirestore/testdata/TestConformance/ActionsOnStructNoRev.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/ActionsWithCompositeID.replay b/docstore/gcpfirestore/testdata/TestConformance/ActionsWithCompositeID.replay
index aeed678980..1004a0e833 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/ActionsWithCompositeID.replay and b/docstore/gcpfirestore/testdata/TestConformance/ActionsWithCompositeID.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/As/verify_As.replay b/docstore/gcpfirestore/testdata/TestConformance/As/verify_As.replay
index 3bf62c7c14..a47e7daa84 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/As/verify_As.replay and b/docstore/gcpfirestore/testdata/TestConformance/As/verify_As.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/As/verify_As_returns_false_when_passed_nil.replay b/docstore/gcpfirestore/testdata/TestConformance/As/verify_As_returns_false_when_passed_nil.replay
index ab3bb81c5c..6a6fad65d6 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/As/verify_As_returns_false_when_passed_nil.replay and b/docstore/gcpfirestore/testdata/TestConformance/As/verify_As_returns_false_when_passed_nil.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/BeforeDo.replay b/docstore/gcpfirestore/testdata/TestConformance/BeforeDo.replay
index 82c05c124d..2a61e3991b 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/BeforeDo.replay and b/docstore/gcpfirestore/testdata/TestConformance/BeforeDo.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/BeforeQuery.replay b/docstore/gcpfirestore/testdata/TestConformance/BeforeQuery.replay
index ac23b70c47..c1f85c5002 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/BeforeQuery.replay and b/docstore/gcpfirestore/testdata/TestConformance/BeforeQuery.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Create.replay b/docstore/gcpfirestore/testdata/TestConformance/Create.replay
index 582d61b269..495507bd4b 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Create.replay and b/docstore/gcpfirestore/testdata/TestConformance/Create.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Data.replay b/docstore/gcpfirestore/testdata/TestConformance/Data.replay
index d52c06e896..8d371361ab 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Data.replay and b/docstore/gcpfirestore/testdata/TestConformance/Data.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Delete.replay b/docstore/gcpfirestore/testdata/TestConformance/Delete.replay
index 4b063a5529..b07e36f13d 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Delete.replay and b/docstore/gcpfirestore/testdata/TestConformance/Delete.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/ExampleInDoc.replay b/docstore/gcpfirestore/testdata/TestConformance/ExampleInDoc.replay
index 9249ac00d3..c041cb10be 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/ExampleInDoc.replay and b/docstore/gcpfirestore/testdata/TestConformance/ExampleInDoc.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Get.replay b/docstore/gcpfirestore/testdata/TestConformance/Get.replay
index 4d496e162b..cf585f3b7e 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Get.replay and b/docstore/gcpfirestore/testdata/TestConformance/Get.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/GetQuery.replay b/docstore/gcpfirestore/testdata/TestConformance/GetQuery.replay
index 09f89a1c38..3adade2d4e 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/GetQuery.replay and b/docstore/gcpfirestore/testdata/TestConformance/GetQuery.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/GetQueryKeyField.replay b/docstore/gcpfirestore/testdata/TestConformance/GetQueryKeyField.replay
index c5f665d07e..abab6d1810 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/GetQueryKeyField.replay and b/docstore/gcpfirestore/testdata/TestConformance/GetQueryKeyField.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/MultipleActions.replay b/docstore/gcpfirestore/testdata/TestConformance/MultipleActions.replay
index d34dda47c8..24bafae5d8 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/MultipleActions.replay and b/docstore/gcpfirestore/testdata/TestConformance/MultipleActions.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Proto.replay b/docstore/gcpfirestore/testdata/TestConformance/Proto.replay
index 1751d8667b..e50a41fbe2 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Proto.replay and b/docstore/gcpfirestore/testdata/TestConformance/Proto.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Put.replay b/docstore/gcpfirestore/testdata/TestConformance/Put.replay
index 6f7e41430e..0517311ecb 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Put.replay and b/docstore/gcpfirestore/testdata/TestConformance/Put.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Replace.replay b/docstore/gcpfirestore/testdata/TestConformance/Replace.replay
index 3b52fc319c..a074a39e87 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Replace.replay and b/docstore/gcpfirestore/testdata/TestConformance/Replace.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/SerializeRevision.replay b/docstore/gcpfirestore/testdata/TestConformance/SerializeRevision.replay
index 8714ca8aec..8f0bbb6cfa 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/SerializeRevision.replay and b/docstore/gcpfirestore/testdata/TestConformance/SerializeRevision.replay differ
diff --git a/docstore/gcpfirestore/testdata/TestConformance/Update.replay b/docstore/gcpfirestore/testdata/TestConformance/Update.replay
index 79379e9ee8..f1c564f58f 100644
Binary files a/docstore/gcpfirestore/testdata/TestConformance/Update.replay and b/docstore/gcpfirestore/testdata/TestConformance/Update.replay differ
diff --git a/docstore/memdocstore/query.go b/docstore/memdocstore/query.go
index 419017b993..72495d5987 100644
--- a/docstore/memdocstore/query.go
+++ b/docstore/memdocstore/query.go
@@ -111,6 +111,8 @@ func applyComparison(op string, c int) bool {
 		return c >= 0
 	case "<=":
 		return c <= 0
+	case "array-contains":
+		return c == 0
 	case "in":
 		return c == 0
 	case "not-in":
@@ -123,6 +125,11 @@ func applyComparison(op string, c int) bool {
 func compare(x1, x2 interface{}) (int, bool) {
 	v1 := reflect.ValueOf(x1)
 	v2 := reflect.ValueOf(x2)
+	// this if for array-contains queries. We are just inverting the parameters x1 and x2 as it's the same logic
+	// as the in/not-in queries.
+	if v1.Kind() == reflect.Slice {
+		return compare(x2, x1)
+	}
 	// this is for in/not-in queries.
 	// return 0 if x1 is in slice x2, -1 if not.
 	if v2.Kind() == reflect.Slice {
diff --git a/docstore/mongodocstore/query.go b/docstore/mongodocstore/query.go
index 0405136990..62cdf6f4ed 100644
--- a/docstore/mongodocstore/query.go
+++ b/docstore/mongodocstore/query.go
@@ -74,13 +74,14 @@ func (c *collection) RunGetQuery(ctx context.Context, q *driver.Query) (driver.D
 }
 
 var mongoQueryOps = map[string]string{
-	driver.EqualOp: "$eq",
-	">":            "$gt",
-	">=":           "$gte",
-	"<":            "$lt",
-	"<=":           "$lte",
-	"in":           "$in",
-	"not-in":       "$nin",
+	driver.EqualOp:   "$eq",
+	">":              "$gt",
+	">=":             "$gte",
+	"<":              "$lt",
+	"<=":             "$lte",
+	"in":             "$in",
+	"not-in":         "$nin",
+	"array-contains": "$eq",
 }
 
 // filtersToBSON converts a []driver.Filter to the MongoDB equivalent, expressed
diff --git a/docstore/query.go b/docstore/query.go
index 847d3ae8cc..17f85ece38 100644
--- a/docstore/query.go
+++ b/docstore/query.go
@@ -37,8 +37,8 @@ func (c *Collection) Query() *Query {
 }
 
 // Where expresses a condition on the query.
-// Valid ops are: "=", ">", "<", ">=", "<=, "in", "not-in".
-// Valid values are strings, integers, floating-point numbers, time.Time and boolean (only for "=", "in" and "not-in") values.
+// Valid ops are: "=", ">", "<", ">=", "<=, "in", "not-in", "array-contains".
+// Valid values are strings, integers, floating-point numbers, and time.Time and boolean (only for "=", "in" and "not-in") values.
 func (q *Query) Where(fp FieldPath, op string, value interface{}) *Query {
 	if q.err != nil {
 		return q
@@ -50,7 +50,7 @@ func (q *Query) Where(fp FieldPath, op string, value interface{}) *Query {
 	}
 	validator, ok := validOp[op]
 	if !ok {
-		return q.invalidf("invalid filter operator: %q. Use one of: =, >, <, >=, <=, in, not-in", op)
+		return q.invalidf("invalid filter operator: %q. Use one of: =, >, <, >=, <=, in, not-in, array-contains", op)
 	}
 	if !validator(value) {
 		return q.invalidf("invalid filter value: %v", value)
@@ -66,13 +66,14 @@ func (q *Query) Where(fp FieldPath, op string, value interface{}) *Query {
 type valueValidator func(interface{}) bool
 
 var validOp = map[string]valueValidator{
-	"=":      validEqualValue,
-	">":      validFilterValue,
-	"<":      validFilterValue,
-	">=":     validFilterValue,
-	"<=":     validFilterValue,
-	"in":     validFilterSlice,
-	"not-in": validFilterSlice,
+	"=":              validEqualValue,
+	">":              validFilterValue,
+	"<":              validFilterValue,
+	">=":             validFilterValue,
+	"<=":             validFilterValue,
+	"array-contains": validFilterValue,
+	"in":             validFilterSlice,
+	"not-in":         validFilterSlice,
 }
 
 func validEqualValue(v interface{}) bool {