diff --git a/cli/tools/registry/pm.rs b/cli/tools/registry/pm.rs
index bd52909980..2060b9a13f 100644
--- a/cli/tools/registry/pm.rs
+++ b/cli/tools/registry/pm.rs
@@ -723,6 +723,10 @@ async fn npm_install_after_modification(
   // npm install
   cache_deps::cache_top_level_deps(&cli_factory, jsr_resolver).await?;
 
+  if let Some(lockfile) = cli_factory.cli_options()?.maybe_lockfile() {
+    lockfile.write_if_changed()?;
+  }
+
   Ok(())
 }
 
diff --git a/tests/specs/add/update_lockfile_if_package_json/__test__.jsonc b/tests/specs/add/update_lockfile_if_package_json/__test__.jsonc
new file mode 100644
index 0000000000..80b35dc3c2
--- /dev/null
+++ b/tests/specs/add/update_lockfile_if_package_json/__test__.jsonc
@@ -0,0 +1,31 @@
+{
+  "tempDir": true,
+  "tests": {
+    "updates_lockfile": {
+      "steps": [
+        {
+          "args": "add npm:@denotest/esm-basic npm:@denotest/say-hello",
+          "output": "add.out"
+        },
+        {
+          "args": [
+            "eval",
+            "console.log(Deno.readTextFileSync('deno.lock'))"
+          ],
+          "output": "lockfile_add.out"
+        },
+        {
+          "args": "remove @denotest/esm-basic @denotest/say-hello",
+          "output": "remove.out"
+        },
+        {
+          "args": [
+            "eval",
+            "console.log(Deno.readTextFileSync('deno.lock'))"
+          ],
+          "output": "lockfile_remove.out"
+        }
+      ]
+    }
+  }
+}
diff --git a/tests/specs/add/update_lockfile_if_package_json/add.out b/tests/specs/add/update_lockfile_if_package_json/add.out
new file mode 100644
index 0000000000..97989b0c38
--- /dev/null
+++ b/tests/specs/add/update_lockfile_if_package_json/add.out
@@ -0,0 +1,5 @@
+[UNORDERED_START]
+Add npm:@denotest/esm-basic@1.0.0
+Add npm:@denotest/say-hello@1.0.0
+[UNORDERED_END]
+[WILDCARD]
\ No newline at end of file
diff --git a/tests/specs/add/update_lockfile_if_package_json/lockfile_add.out b/tests/specs/add/update_lockfile_if_package_json/lockfile_add.out
new file mode 100644
index 0000000000..d452c2de82
--- /dev/null
+++ b/tests/specs/add/update_lockfile_if_package_json/lockfile_add.out
@@ -0,0 +1,7 @@
+{
+  "version": "4",
+  "specifiers": {
+    "npm:@denotest/esm-basic@1": "1.0.0",
+    "npm:@denotest/say-hello@1": "1.0.0"
+  },
+[WILDCARD]
diff --git a/tests/specs/add/update_lockfile_if_package_json/lockfile_remove.out b/tests/specs/add/update_lockfile_if_package_json/lockfile_remove.out
new file mode 100644
index 0000000000..fdd4f1cc60
--- /dev/null
+++ b/tests/specs/add/update_lockfile_if_package_json/lockfile_remove.out
@@ -0,0 +1,4 @@
+{
+  "version": "4"
+}
+
diff --git a/tests/specs/add/update_lockfile_if_package_json/package.json b/tests/specs/add/update_lockfile_if_package_json/package.json
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/specs/add/update_lockfile_if_package_json/remove.out b/tests/specs/add/update_lockfile_if_package_json/remove.out
new file mode 100644
index 0000000000..8efb0810cf
--- /dev/null
+++ b/tests/specs/add/update_lockfile_if_package_json/remove.out
@@ -0,0 +1,4 @@
+[UNORDERED_START]
+Removed @denotest/esm-basic
+Removed @denotest/say-hello
+[UNORDERED_END]