diff --git a/R/addIndex.R b/R/addIndex.R
index 75d7d24..311d3e7 100644
--- a/R/addIndex.R
+++ b/R/addIndex.R
@@ -2,7 +2,8 @@
 #'
 #' @description
 #' Adds an index on subject_id and cohort_start_date to a cohort table. Note,
-#' currently only indexes will be added if the table is in a postgres database.
+#' currently only indexes will be added if the table is in a postgres or sql
+#' server database.
 #'
 #' @inheritParams cohortDoc
 #'
@@ -67,6 +68,56 @@ addIndex <- function(cdm, name, cols) {
       ");"
     )
     suppressMessages(DBI::dbExecute(con, query))
+  } else if (dbType == c("sql server")) {
+    con <- attr(cdm, "dbcon")
+    schema <- attr(cdm, "write_schema")
+    if(length(schema) > 2){
+      prefix <- attr(cdm, "write_schema")["prefix"]
+      schema1 <- attr(cdm, "write_schema")["schema1"]
+      schema2 <- attr(cdm, "write_schema")["schema2"]
+    } else {
+      schema1 <- attr(cdm, "write_schema")["schema1"]
+      schema2 <- attr(cdm, "write_schema")["schema2"]
+      prefix <- NULL
+    }
+
+    existingIndex <- DBI::dbGetQuery(con,
+                                     paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         DB_NAME() AS database_name
+  FROM sys.indexes i
+  JOIN sys.objects o ON o.object_id = o.object_id
+  WHERE o.name = '", paste0(prefix, name) ,"'
+  AND i.name IS NOT NULL
+
+  UNION ALL
+
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = '", paste0(prefix, name) ,"'
+  AND i.name IS NOT NULL
+"))
+
+
+    if(nrow(existingIndex) > 0){
+      cli::cli_inform("Index already existing so no new index added.")
+      return(invisible(NULL))
+    } else {
+      cli::cli_inform("Adding indexes to table")
+    }
+
+    cols <- paste0(cols, collapse = ",")
+
+    query <- paste0(
+      "CREATE INDEX IX_", name, "_", gsub(",", "_", cols),
+      " ON ", schema1, ".", schema2, ".", prefix, name,
+      " (", cols, ");"
+    )
+    suppressMessages(DBI::dbExecute(con, query))
   }
 
   return(invisible(NULL))
diff --git a/man/addCohortTableIndex.Rd b/man/addCohortTableIndex.Rd
index c652c03..d7238bd 100644
--- a/man/addCohortTableIndex.Rd
+++ b/man/addCohortTableIndex.Rd
@@ -14,5 +14,6 @@ The cohort table
 }
 \description{
 Adds an index on subject_id and cohort_start_date to a cohort table. Note,
-currently only indexes will be added if the table is in a postgres database.
+currently only indexes will be added if the table is in a postgres or sql
+server database.
 }
diff --git a/tests/testthat/test-addIndex.R b/tests/testthat/test-addIndex.R
index 7a653c9..6868afd 100644
--- a/tests/testthat/test-addIndex.R
+++ b/tests/testthat/test-addIndex.R
@@ -68,3 +68,172 @@ test_that("postgres test - adds indexes", {
   CDMConnector::cdm_disconnect(cdm = cdm)
 
 })
+
+test_that("sql server test - adds indexes", {
+  skip_on_cran()
+  skip_if(Sys.getenv("CDM5_SQL_SERVER_SERVER") == "")
+
+  db <- DBI::dbConnect(odbc::odbc(),
+                       Driver   = Sys.getenv("SQL_SERVER_DRIVER"),
+                       Server   = Sys.getenv("CDM5_SQL_SERVER_SERVER"),
+                       Database = Sys.getenv("CDM5_SQL_SERVER_CDM_DATABASE"),
+                       UID      = Sys.getenv("CDM5_SQL_SERVER_USER"),
+                       PWD      = Sys.getenv("CDM5_SQL_SERVER_PASSWORD"),
+                       TrustServerCertificate="yes",
+                       Port     = Sys.getenv("CDM5_SQL_SERVER_PORT"))
+
+  cdm <- CDMConnector::cdm_from_con(
+    con = db,
+    cdm_schema = strsplit(Sys.getenv("CDM5_SQL_SERVER_CDM_SCHEMA"), "\\.")[[1]],
+    write_schema = c(schema =  strsplit(Sys.getenv("CDM5_SQL_SERVER_SCRATCH_SCHEMA"), "\\.")[[1]],
+                     prefix = "cc_")
+  )
+
+  cdm <- omopgenerics::insertTable(cdm = cdm,
+                                   name = "my_cohort",
+                                   table = data.frame(cohort_definition_id = 1L,
+                                                      subject_id = 1L,
+                                                      cohort_start_date = as.Date("2009-01-01"),
+                                                      cohort_end_date = as.Date("2009-01-02")))
+  cdm$my_cohort <- omopgenerics::newCohortTable(cdm$my_cohort)
+
+  indexes_start <- DBI::dbGetQuery(db,
+                                 paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'cc_my_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_start) == 0)
+
+  cdm$my_cohort <- cdm$my_cohort |> addCohortTableIndex()
+
+  indexes_end <- DBI::dbGetQuery(db,
+                                   paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'cc_my_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_end) == 1)
+
+  # no error if we add another index - it will just be skipped
+  cdm$my_cohort <- cdm$my_cohort |> addCohortTableIndex()
+  indexes_end_2 <- DBI::dbGetQuery(db,
+                                 paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'cc_my_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_end_2) == 1)
+
+  # should still all work as before
+  cdm$my_cohort <- omopgenerics::newCohortTable(cdm$my_cohort)
+  omopgenerics::dropTable(cdm = cdm, name = "my_cohort")
+
+
+  # no cdm prefix
+  cdm <- CDMConnector::cdm_from_con(
+    con = db,
+    cdm_schema = strsplit(Sys.getenv("CDM5_SQL_SERVER_CDM_SCHEMA"), "\\.")[[1]],
+    write_schema = c(schema =  strsplit(Sys.getenv("CDM5_SQL_SERVER_SCRATCH_SCHEMA"), "\\.")[[1]])
+  )
+  cdm <- omopgenerics::insertTable(cdm = cdm,
+                                   name = "my_new_cohort",
+                                   table = data.frame(cohort_definition_id = 1L,
+                                                      subject_id = 1L,
+                                                      cohort_start_date = as.Date("2009-01-01"),
+                                                      cohort_end_date = as.Date("2009-01-02")))
+  cdm$my_new_cohort <- omopgenerics::newCohortTable(cdm$my_new_cohort)
+  cdm$my_new_cohort <- cdm$my_new_cohort |> addCohortTableIndex()
+
+  omopgenerics::dropTable(cdm = cdm, name = "my_new_cohort")
+
+  CDMConnector::cdm_disconnect(cdm = cdm)
+
+})
+
+test_that("sql server no prefix test - adds indexes", {
+  skip_on_cran()
+  skip_if(Sys.getenv("CDM5_SQL_SERVER_SERVER") == "")
+
+  db <- DBI::dbConnect(odbc::odbc(),
+                       Driver   = Sys.getenv("SQL_SERVER_DRIVER"),
+                       Server   = Sys.getenv("CDM5_SQL_SERVER_SERVER"),
+                       Database = Sys.getenv("CDM5_SQL_SERVER_CDM_DATABASE"),
+                       UID      = Sys.getenv("CDM5_SQL_SERVER_USER"),
+                       PWD      = Sys.getenv("CDM5_SQL_SERVER_PASSWORD"),
+                       TrustServerCertificate="yes",
+                       Port     = Sys.getenv("CDM5_SQL_SERVER_PORT"))
+
+
+  # no cdm prefix
+  cdm <- CDMConnector::cdm_from_con(
+    con = db,
+    cdm_schema = strsplit(Sys.getenv("CDM5_SQL_SERVER_CDM_SCHEMA"), "\\.")[[1]],
+    write_schema = c(schema =  strsplit(Sys.getenv("CDM5_SQL_SERVER_SCRATCH_SCHEMA"), "\\.")[[1]])
+  )
+  cdm <- omopgenerics::insertTable(cdm = cdm,
+                                   name = "my_new_cohort",
+                                   table = data.frame(cohort_definition_id = 1L,
+                                                      subject_id = 1L,
+                                                      cohort_start_date = as.Date("2009-01-01"),
+                                                      cohort_end_date = as.Date("2009-01-02")))
+  cdm$my_new_cohort <- omopgenerics::newCohortTable(cdm$my_new_cohort)
+
+  indexes_start <- DBI::dbGetQuery(db,
+                                   paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'my_new_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_start) == 0)
+
+  cdm$my_new_cohort <- cdm$my_new_cohort |> addCohortTableIndex()
+
+  indexes_end <- DBI::dbGetQuery(db,
+                                   paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'my_new_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_end) == 1)
+
+  # skip creation now index exists
+  cdm$my_new_cohort <- cdm$my_new_cohort |> addCohortTableIndex()
+
+  indexes_end_2 <- DBI::dbGetQuery(db,
+                                 paste0("
+  SELECT i.name AS index_name,
+         o.name AS table_name,
+         'tempdb' AS database_name
+  FROM tempdb.sys.indexes i
+  JOIN tempdb.sys.objects o ON i.object_id = o.object_id
+  WHERE o.name = 'my_new_cohort'
+  AND i.name IS NOT NULL
+"))
+  expect_true(nrow(indexes_end_2) == 1)
+
+  omopgenerics::dropTable(cdm = cdm, name = "my_new_cohort")
+
+  CDMConnector::cdm_disconnect(cdm = cdm)
+
+})