diff --git a/src/common/connection.ts b/src/common/connection.ts
index 009ced86..e2cb5913 100644
--- a/src/common/connection.ts
+++ b/src/common/connection.ts
@@ -475,13 +475,17 @@ class Connection extends EventEmitter {
   _send(message: string): Promise<void> {
     this._trace('send', message)
     return new Promise((resolve, reject) => {
-      this._ws.send(message, undefined, error => {
-        if (error) {
-          reject(new DisconnectedError(error.message, error))
-        } else {
-          resolve()
-        }
-      })
+      try {
+        this._ws.send(message, undefined, error => {
+          if (error) {
+            reject(new DisconnectedError(error.message, error))
+          } else {
+            resolve()
+          }
+        })
+      } catch (error) {
+        reject(new DisconnectedError(error.message, error))
+      }
     })
   }
 
diff --git a/test/connection-test.ts b/test/connection-test.ts
index 88428f56..32956476 100644
--- a/test/connection-test.ts
+++ b/test/connection-test.ts
@@ -201,6 +201,30 @@ describe('Connection', function() {
       })
   })
 
+  it('DisconnectedError on initial _onOpen send', async function() {
+    // _onOpen previously could throw PromiseRejectionHandledWarning: Promise rejection was handled asynchronously
+    // do not rely on the api.setup hook to test this as it bypasses the case, disconnect api connection first
+    await this.api.disconnect();
+
+    // stub _onOpen to only run logic relevant to test case
+    this.api.connection._onOpen = () => {
+      // overload websocket send on open when _ws exists
+      this.api.connection._ws.send = function(data, options, cb) {
+        // recent ws throws this error instead of calling back
+        throw new Error('WebSocket is not open: readyState 0 (CONNECTING)');
+      }
+      const request = {command: 'subscribe', streams: ['ledger']};
+      return this.api.connection.request(request);
+    }
+
+    try {
+      await this.api.connect();
+    } catch (error) {
+      assert(error instanceof this.api.errors.DisconnectedError);
+      assert.strictEqual(error.message, 'WebSocket is not open: readyState 0 (CONNECTING)');
+    }
+  });
+
   it('ResponseFormatError', function() {
     this.api.connection._send = function(message) {
       const parsed = JSON.parse(message)