diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b8ce019..37cc8e97 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+# v7.2.0 (Not released yet)
+
+Added
+- Support for `Query\Builder::upsert()` (#203)
+
 # v7.1.0 (2024-03-11)
 
 Changed
diff --git a/phpstan.neon b/phpstan.neon
index d42e5cff..e0d4e541 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -41,3 +41,6 @@ parameters:
         - message: "#^Method Colopl\\\\Spanner\\\\SpannerServiceProvider\\:\\:parseConfig\\(\\) should return array\\{name\\: string, instance\\: string, database\\: string, prefix\\: string, cache_path\\: string|null, session_pool\\: array\\<string, mixed\\>\\} but returns non\\-empty\\-array\\<string, mixed\\>\\.$#"
           count: 1
           path: src/SpannerServiceProvider.php
+        - message: "#^Expression on left side of \\?\\? is not nullable\\.$#"
+          count: 1
+          path: src/Connection.php
diff --git a/src/Connection.php b/src/Connection.php
index 2876c052..4a1f115a 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -28,6 +28,7 @@
 use Exception;
 use Generator;
 use Google\Cloud\Core\Exception\AbortedException;
+use Google\Cloud\Core\Exception\ConflictException;
 use Google\Cloud\Core\Exception\GoogleException;
 use Google\Cloud\Core\Exception\NotFoundException;
 use Google\Cloud\Spanner\Database;
@@ -323,11 +324,9 @@ public function affectingStatement($query, $bindings = []): int
                     throw new RuntimeException('Tried to run update outside of transaction! Affecting statements must be done inside a transaction');
                 }
 
-                $rowCount = $transaction->executeUpdate($query, ['parameters' => $this->prepareBindings($bindings)]);
-
-                $this->recordsHaveBeenModified($rowCount > 0);
-
-                return $rowCount;
+                return $this->shouldRunAsBatchDml($query)
+                    ? $this->executeBatchDml($transaction, $query, $bindings)
+                    : $this->executeDml($transaction, $query, $bindings);
             });
         };
 
@@ -595,6 +594,55 @@ protected function executePartitionedQuery(string $query, array $options): Gener
         }
     }
 
+    /**
+     * @param Transaction $transaction
+     * @param string $query
+     * @param list<mixed> $bindings
+     * @return int
+     */
+    protected function executeDml(Transaction $transaction, string $query, array $bindings = []): int
+    {
+        $rowCount = $transaction->executeUpdate($query, ['parameters' => $this->prepareBindings($bindings)]);
+        $this->recordsHaveBeenModified($rowCount > 0);
+        return $rowCount;
+    }
+
+    /**
+     * @param Transaction $transaction
+     * @param string $query
+     * @param list<mixed> $bindings
+     * @return int
+     */
+    protected function executeBatchDml(Transaction $transaction, string $query, array $bindings = []): int
+    {
+        $result = $transaction->executeUpdateBatch([
+            ['sql' => $query, 'parameters' => $this->prepareBindings($bindings)]
+        ]);
+
+        $error = $result->error();
+        if ($error !== null) {
+            throw new ConflictException(
+                $error['status']['message'] ?? '',
+                $error['status']['code'] ?? 0,
+                null,
+                ['details' => $error['details'] ?? []],
+            );
+        }
+
+        $rowCount = array_sum($result->rowCounts() ?? []);
+        $this->recordsHaveBeenModified($rowCount > 0);
+        return $rowCount;
+    }
+
+    /**
+     * @param string $query
+     * @return bool
+     */
+    protected function shouldRunAsBatchDml(string $query): bool
+    {
+        return stripos($query, 'insert or ') === 0;
+    }
+
     /**
      * @template T
      * @param Closure(): T $callback
diff --git a/src/Query/Builder.php b/src/Query/Builder.php
index 948df960..7f13f86b 100644
--- a/src/Query/Builder.php
+++ b/src/Query/Builder.php
@@ -17,6 +17,7 @@
 
 namespace Colopl\Spanner\Query;
 
+use Closure;
 use Colopl\Spanner\Connection;
 use Illuminate\Contracts\Support\Arrayable;
 use Illuminate\Database\Query\Builder as BaseBuilder;
@@ -55,6 +56,33 @@ public function updateOrInsert(array $attributes, array $values = [])
         return (bool) $this->take(1)->update(Arr::except($values, array_keys($attributes)));
     }
 
+    /**
+     * @inheritDoc
+     */
+    public function upsert(array $values, $uniqueBy = [], $update = null)
+    {
+        if (empty($values)) {
+            return 0;
+        }
+
+        if (! array_is_list($values)) {
+            $values = [$values];
+        } else {
+            foreach ($values as $key => $value) {
+                ksort($value);
+
+                $values[$key] = $value;
+            }
+        }
+
+        $this->applyBeforeQueryCallbacks();
+
+        return $this->connection->affectingStatement(
+            $this->grammar->compileUpsert($this, $values, [], []),
+            $this->cleanBindings(Arr::flatten($values, 1)),
+        );
+    }
+
     /**
      * @inheritDoc
      */
diff --git a/src/Query/Concerns/UsesMutations.php b/src/Query/Concerns/UsesMutations.php
index 7d1afbf4..56f11522 100644
--- a/src/Query/Concerns/UsesMutations.php
+++ b/src/Query/Concerns/UsesMutations.php
@@ -26,21 +26,21 @@
 trait UsesMutations
 {
     /**
-     * @param array $values
+     * @param array<string, mixed> $values
      * @return void
      */
     public function insertUsingMutation(array $values)
     {
-        $this->connection->insertUsingMutation($this->from, $values);
+        $this->connection->insertUsingMutation($this->getTableName(), $values);
     }
 
     /**
-     * @param array $values
+     * @param array<string, mixed> $values
      * @return void
      */
     public function updateUsingMutation(array $values)
     {
-        $this->connection->updateUsingMutation($this->from, $values);
+        $this->connection->updateUsingMutation($this->getTableName(), $values);
     }
 
     /**
@@ -49,15 +49,23 @@ public function updateUsingMutation(array $values)
      */
     public function insertOrUpdateUsingMutation(array $values)
     {
-        $this->connection->insertOrUpdateUsingMutation($this->from, $values);
+        $this->connection->insertOrUpdateUsingMutation($this->getTableName(), $values);
     }
 
     /**
-     * @param array|KeySet $keys
+     * @param list<string>|KeySet $keys
      * @return void
      */
     public function deleteUsingMutation($keys)
     {
-        $this->connection->deleteUsingMutation($this->from, $keys);
+        $this->connection->deleteUsingMutation($this->getTableName(), $keys);
+    }
+
+    /**
+     * @return string
+     */
+    private function getTableName(): string
+    {
+        return (string) $this->getGrammar()->getValue($this->from);
     }
 }
diff --git a/src/Query/Grammar.php b/src/Query/Grammar.php
index bc2c9af3..6927adbc 100644
--- a/src/Query/Grammar.php
+++ b/src/Query/Grammar.php
@@ -22,6 +22,7 @@
 use Illuminate\Database\Query\Builder;
 use Illuminate\Contracts\Database\Query\Expression;
 use Illuminate\Database\Query\Grammars\Grammar as BaseGrammar;
+use Illuminate\Support\Str;
 use RuntimeException;
 
 class Grammar extends BaseGrammar
@@ -29,6 +30,14 @@ class Grammar extends BaseGrammar
     use MarksAsNotSupported;
     use SharedGrammarCalls;
 
+    /**
+     * @inheritDoc
+     */
+    public function compileUpsert(Builder $query, array $values, array $uniqueBy, array $update)
+    {
+        return Str::replaceFirst('insert', 'insert or update', $this->compileInsert($query, $values));
+    }
+
     /**
      * @inheritDoc
      */
diff --git a/tests/Query/BuilderTest.php b/tests/Query/BuilderTest.php
index 8cadfc97..a6790737 100644
--- a/tests/Query/BuilderTest.php
+++ b/tests/Query/BuilderTest.php
@@ -22,12 +22,11 @@
 use Colopl\Spanner\Schema\Blueprint;
 use Colopl\Spanner\Tests\TestCase;
 use Colopl\Spanner\TimestampBound\ExactStaleness;
+use Google\Cloud\Core\Exception\ConflictException;
 use Google\Cloud\Spanner\Bytes;
 use Google\Cloud\Spanner\Duration;
-use Illuminate\Support\Str;
 use Illuminate\Database\QueryException;
 use Illuminate\Support\Carbon;
-use Illuminate\Support\Collection;
 use LogicException;
 
 use const Grpc\STATUS_ALREADY_EXISTS;
@@ -578,6 +577,78 @@ public function testInsertDatetime(): void
         $this->assertSame($carbonMax->getTimestamp(), $insertedTimestamp->getTimestamp());
     }
 
+    public function test_upsert_single_row(): void
+    {
+        $table = __FUNCTION__;
+        $conn = $this->getDefaultConnection();
+        $sb = $conn->getSchemaBuilder();
+        $sb->create($table, function (Blueprint $table) {
+            $table->integer('id')->primary();
+            $table->string('s', 1);
+        });
+
+        $query = $conn->table($table);
+        $this->assertSame(1, $query->upsert(['id' => 1, 's' => 'a']));
+        $this->assertSame(1, $query->upsert(['id' => 1, 's' => 'b']));
+
+        $this->assertSame(['id' => 1, 's' => 'b'], (array) $query->sole());
+    }
+
+    public function test_upsert_multi_row(): void
+    {
+        $table = __FUNCTION__;
+        $conn = $this->getDefaultConnection();
+        $sb = $conn->getSchemaBuilder();
+        $sb->create($table, function (Blueprint $table) {
+            $table->integer('id')->primary();
+            $table->string('s', 1);
+        });
+
+        $query = $conn->table($table);
+
+        // insert
+        $this->assertSame(2, $query->upsert([
+            ['id' => 1, 's' => 'a'],
+            ['id' => 2, 's' => 'b'],
+        ]));
+
+        // update (no change x1, change x1, insert x1)
+        $this->assertSame(3, $query->upsert([
+            ['id' => 1, 's' => 'a'],
+            ['id' => 2, 's' => '_'],
+            ['id' => 3, 's' => 'c'],
+        ]));
+
+        $this->assertSame(['a', '_', 'c'], $query->orderBy('id')->pluck('s')->all());
+    }
+
+    public function test_upsert_throw_error(): void
+    {
+        $table = __FUNCTION__;
+        $conn = $this->getDefaultConnection();
+        $sb = $conn->getSchemaBuilder();
+        $sb->create($table, function (Blueprint $table) {
+            $table->integer('id')->primary();
+            $table->string('s', 1);
+        });
+
+        $query = $conn->table($table);
+        $exceptionThrown = false;
+        try {
+            $query->upsert([
+                ['id' => 1, 's' => 'a'],
+                ['id' => 2, 's' => 'bb'],
+            ]);
+        } catch (QueryException $e) {
+            $this->assertSame(9, $e->getCode());
+            $this->assertStringContainsString('New value exceeds the maximum size limit', $e->getMessage());
+            $exceptionThrown = true;
+        }
+
+        $this->assertTrue($exceptionThrown);
+        $this->assertSame(0, $query->count());
+    }
+
     public function testWhereDatetime(): void
     {
         date_default_timezone_set('Asia/Tokyo');
@@ -818,7 +889,7 @@ public function test_whereLike(): void
             $caughtException = $ex;
         }
         if (getenv('SPANNER_EMULATOR_HOST')) {
-            $this->assertStringContainsString('INTERNAL', $caughtException?->getMessage());
+            $this->assertStringContainsString('Invalid UTF-8', $caughtException?->getMessage());
         } else {
             $this->assertStringContainsString('Invalid request proto: an error was encountered during deserialization of the request proto.', $caughtException?->getMessage());
         }