diff --git a/src/serialmonitor/serialMonitor.ts b/src/serialmonitor/serialMonitor.ts
index 2dc847b4..64f2ecb1 100644
--- a/src/serialmonitor/serialMonitor.ts
+++ b/src/serialmonitor/serialMonitor.ts
@@ -61,6 +61,8 @@ export class SerialMonitor implements vscode.Disposable {
         });
 
         this.serialMonitorApi = await getSerialMonitorApi(Version.latest, extensionContext);
+
+        this.checkForUndefinedSerialMonitorApi();
     }
 
     public get initialized(): boolean {
@@ -68,6 +70,8 @@ export class SerialMonitor implements vscode.Disposable {
     }
 
     public async selectSerialPort(): Promise<string | undefined> {
+        this.checkForUndefinedSerialMonitorApi(true);
+
         const ports = await this.serialMonitorApi.listAvailablePorts();
         if (!ports.length) {
             vscode.window.showInformationMessage("No serial port is available.");
@@ -113,6 +117,8 @@ export class SerialMonitor implements vscode.Disposable {
     }
 
     public async openSerialMonitor(restore: boolean = false): Promise<void> {
+        this.checkForUndefinedSerialMonitorApi(true);
+
         if (!this.currentPort) {
             const ans = await vscode.window.showInformationMessage("No serial port was selected, please select a serial port first", "Select", "Cancel");
             if (ans === "Select") {
@@ -151,6 +157,8 @@ export class SerialMonitor implements vscode.Disposable {
     }
 
     public async closeSerialMonitor(port?: string): Promise<boolean> {
+        this.checkForUndefinedSerialMonitorApi(true);
+
         const portToClose = port ?? this.currentPort;
         let closed = false;
         if (portToClose) {
@@ -165,6 +173,17 @@ export class SerialMonitor implements vscode.Disposable {
         this.serialMonitorApi.dispose();
     }
 
+    private checkForUndefinedSerialMonitorApi(showError: boolean = false): void {
+        const errorString = "Serial Monitor API was not retrieved. You may not have the most recent version of the Serial Monitor extension installed.";
+        if (this.serialMonitorApi === undefined) {
+            if (showError) {
+                Logger.notifyUserError("UndefinedSerialMonitorApi", new Error(errorString));
+            } else {
+                Logger.traceError("UndefinedSerialMonitorApi", new Error(errorString));
+            }
+        }
+    }
+
     private updatePortListStatus(port?: string) {
         const dc = DeviceContext.getInstance();
         if (port) {