diff --git a/cli/tests/testdata/tls/invalid.crt b/cli/tests/testdata/tls/invalid.crt
new file mode 100644
index 0000000000..688e32ede7
--- /dev/null
+++ b/cli/tests/testdata/tls/invalid.crt
@@ -0,0 +1,3 @@
+-----BEGIN CERTIFICATE-----
+INVALID
+-----END CERTIFICATE-----
diff --git a/cli/tests/testdata/tls/invalid.key b/cli/tests/testdata/tls/invalid.key
new file mode 100644
index 0000000000..b57bc2f68e
--- /dev/null
+++ b/cli/tests/testdata/tls/invalid.key
@@ -0,0 +1,3 @@
+-----BEGIN PRIVATE KEY-----
+INVALID
+-----END PRIVATE KEY-----
diff --git a/cli/tests/unit/tls_test.ts b/cli/tests/unit/tls_test.ts
index 1f0702f623..8162c53b56 100644
--- a/cli/tests/unit/tls_test.ts
+++ b/cli/tests/unit/tls_test.ts
@@ -1491,3 +1491,31 @@ Deno.test({
   });
   listener.close();
 });
+
+Deno.test(
+  { permissions: { net: true, read: true } },
+  function listenTLSInvalidCert() {
+    assertThrows(() => {
+      Deno.listenTls({
+        hostname: "localhost",
+        port: 3500,
+        certFile: "cli/tests/testdata/tls/invalid.crt",
+        keyFile: "cli/tests/testdata/tls/localhost.key",
+      });
+    }, Deno.errors.InvalidData);
+  },
+);
+
+Deno.test(
+  { permissions: { net: true, read: true } },
+  function listenTLSInvalidKey() {
+    assertThrows(() => {
+      Deno.listenTls({
+        hostname: "localhost",
+        port: 3500,
+        certFile: "cli/tests/testdata/tls/localhost.crt",
+        keyFile: "cli/tests/testdata/tls/invalid.key",
+      });
+    }, Deno.errors.InvalidData);
+  },
+);
diff --git a/ext/net/ops_tls.rs b/ext/net/ops_tls.rs
index ac9c80f7a5..7b1cb4e0a5 100644
--- a/ext/net/ops_tls.rs
+++ b/ext/net/ops_tls.rs
@@ -1055,7 +1055,13 @@ where
     .with_safe_defaults()
     .with_no_client_auth()
     .with_single_cert(cert_chain, key_der)
-    .expect("invalid key or certificate");
+    .map_err(|e| {
+      custom_error(
+        "InvalidData",
+        format!("Error creating TLS certificate: {:?}", e),
+      )
+    })?;
+
   if let Some(alpn_protocols) = args.alpn_protocols {
     tls_config.alpn_protocols =
       alpn_protocols.into_iter().map(|s| s.into_bytes()).collect();