diff --git a/NEWS.md b/NEWS.md
index f885fe5d..8ab06134 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # connectapi (development version)
 
+- Added a single retry to `content_restart()` to more robustly clean up
+  temporary environment variables. (#498)
+
 # connectapi 0.10.0
 
 - Removed `prefix` argument to `connect()` function, which was a convenience utility for testing. (#477)
diff --git a/R/content.R b/R/content.R
index 22efc210..486c7e39 100644
--- a/R/content.R
+++ b/R/content.R
@@ -1434,7 +1434,38 @@ content_restart <- function(content) {
   # https://rlang.r-lib.org/reference/glue-operators.html#using-glue-syntax-in-packages
   env_var_name <- glue::glue("_CONNECT_RESTART_{unix_epoch_in_seconds}")
   content$environment_set("{env_var_name}" := unix_epoch_in_seconds)
-  content$environment_set("{env_var_name}" := NA)
+  tryCatch(
+    {
+      content$environment_set("{env_var_name}" := NA)
+    },
+    error = function(e) {
+      # we sometimes see the rapid set/unset lead to failures, which leave the
+      # env var in place. If we get a 500 error, wait a second and try one more
+      # time
+      if (grepl("500", conditionMessage(e))) {
+        Sys.sleep(1)
+        tryCatch(
+          content$environment_set("{env_var_name}" := NA),
+          error = function(e) {
+            warning(
+              glue::glue(
+                "Restarted content by setting environment variable {env_var_name}, but was unable to clean it up. See ?set_environment_remove for how to manually remove this variable."
+              ),
+              call. = FALSE
+            )
+          }
+        )
+      } else {
+        warning(
+          glue::glue(
+            "Restarted content by setting environment variable {env_var_name}, but was unable to clean it up. See ?set_environment_remove for how to manually remove this variable."
+          ),
+          call. = FALSE
+        )
+      }
+    }
+  )
+
   # nolint end
   invisible(NULL)
 }
diff --git a/tests/testthat/test-content.R b/tests/testthat/test-content.R
index bdc9b4e4..164e4706 100644
--- a/tests/testthat/test-content.R
+++ b/tests/testthat/test-content.R
@@ -662,3 +662,99 @@ test_that("lock_content() and unlock_content() error on Connect < 2024.08.0", {
     "ERROR: This feature requires Posit Connect version 2024.08.0 but you are using 2024.07.0."
   )
 })
+
+test_that("content_restart retries if delete fails", {
+  mock_connect <- MockConnect$new("2025.09.0")
+  mock_connect$mock_response(
+    "GET",
+    "v1/content/test-guid",
+    content = list(
+      guid = "test-guid",
+      name = "test-content",
+      title = "Test Content",
+      app_mode = "shiny",
+      content_url = "https://connect.example/content/test-guid/",
+      dashboard_url = "https://connect.example/connect/#/apps/test-guid"
+    )
+  )
+
+  # First PATCH to set the env var (succeeds)
+  mock_connect$mock_response(
+    "PATCH",
+    "v1/content/test-guid/environment",
+    content = list(),
+    status_code = 200L
+  )
+
+  # Second PATCH to delete the env var (fails with 500)
+  mock_connect$mock_response(
+    "PATCH",
+    "v1/content/test-guid/environment",
+    content = list(error = "Internal server error"),
+    status_code = 500L
+  )
+
+  # Third PATCH to delete the env var (retry succeeds)
+  mock_connect$mock_response(
+    "PATCH",
+    "v1/content/test-guid/environment",
+    content = list(),
+    status_code = 200L
+  )
+
+  # Get the content item
+  item <- content_item(mock_connect, "test-guid")
+
+  expect_no_error(content_restart(item))
+  expect_equal(
+    mock_connect$call_log,
+    c(
+      "GET https://connect.example/__api__/v1/content/test-guid",
+      "PATCH https://connect.example/__api__/v1/content/test-guid/environment",
+      "PATCH https://connect.example/__api__/v1/content/test-guid/environment",
+      "PATCH https://connect.example/__api__/v1/content/test-guid/environment"
+    )
+  )
+})
+
+test_that("content_restart doesn't retry if error isn't a 500", {
+  mock_connect <- MockConnect$new("2025.09.0")
+  mock_connect$mock_response(
+    "GET",
+    "v1/content/test-guid",
+    content = list(
+      guid = "test-guid",
+      name = "test-content",
+      title = "Test Content",
+      app_mode = "shiny",
+      content_url = "https://connect.example/content/test-guid/",
+      dashboard_url = "https://connect.example/connect/#/apps/test-guid"
+    )
+  )
+
+  mock_connect$mock_response(
+    "PATCH",
+    "v1/content/test-guid/environment",
+    content = list(),
+    status_code = 200L
+  )
+
+  mock_connect$mock_response(
+    "PATCH",
+    "v1/content/test-guid/environment",
+    content = list(error = "Bad request"),
+    status_code = 400L
+  )
+
+  item <- content_item(mock_connect, "test-guid")
+  expect_warning(content_restart(item))
+  # only 2 PATCHes
+  expect_equal(
+    mock_connect$call_log,
+    c(
+      "GET https://connect.example/__api__/v1/content/test-guid",
+      "PATCH https://connect.example/__api__/v1/content/test-guid/environment",
+      "PATCH https://connect.example/__api__/v1/content/test-guid/environment"
+    )
+  )
+})