diff --git a/.changeset/shaggy-drinks-develop.md b/.changeset/shaggy-drinks-develop.md
new file mode 100644
index 0000000..b59b699
--- /dev/null
+++ b/.changeset/shaggy-drinks-develop.md
@@ -0,0 +1,5 @@
+---
+"terminal-keeper": patch
+---
+
+fix: warn if the folder is not opened before using Terminal Keeper.
diff --git a/src/commands/generateAsync.ts b/src/commands/generateAsync.ts
index 54fb140..59343be 100644
--- a/src/commands/generateAsync.ts
+++ b/src/commands/generateAsync.ts
@@ -1,11 +1,30 @@
-import { window } from 'vscode';
+import { commands, window } from 'vscode';
 import { Configuration } from '../configuration/configuration';
 import { configurationTemplate } from '../configuration/template';
-import { constants } from '../utils/constants';
-import { showErrorMessageWithDetail, showTextDocument } from '../utils/utils';
+import { constants, sysCommands } from '../utils/constants';
+import { isWorkspaceOpened, showErrorMessageWithDetail, showTextDocument } from '../utils/utils';
 
 export const generateAsync = async (): Promise<void> => {
     try {
+        // Check workspace is opened
+        if (!isWorkspaceOpened()) {
+            window
+                .showInformationMessage(
+                    constants.openWorkspace,
+                    constants.openFolderButton,
+                    constants.openWorkspaceButton
+                )
+                .then(async (selection) => {
+                    if (selection === constants.openFolderButton) {
+                        await commands.executeCommand(sysCommands.openFolder);
+                    }
+                    if (selection === constants.openWorkspaceButton) {
+                        await commands.executeCommand(sysCommands.openWorkspace);
+                    }
+                });
+            return;
+        }
+
         // Write configuration file
         const configInstance = Configuration.instance();
         const isDefinedSessionFile = await configInstance.isDefinedSessionFile();
diff --git a/src/utils/constants.ts b/src/utils/constants.ts
index 5025515..63ab4d3 100644
--- a/src/utils/constants.ts
+++ b/src/utils/constants.ts
@@ -12,12 +12,18 @@ export const extCommands = {
     activeTerminalActivity: 'terminal-keeper.active-terminal-activity'
 };
 
+export const sysCommands = {
+    openFolder: 'workbench.action.files.openFolder',
+    openWorkspace: 'workbench.action.openWorkspace'
+};
+
 export const constants = {
     // Common
     defaultSession: 'default',
 
     // Open the configuration file
     openConfigurationFailed: 'Failed to open the configuration file!',
+    openWorkspace: 'Please make sure to open a workspace folder before using Terminal Keeper!',
 
     // Generate the configuration file
     generateConfigurationTitle: 'Would you like to generate the configuration?',
@@ -66,5 +72,7 @@ export const constants = {
     noButton: 'No',
     newSession: 'Create a new session...',
     viewConfigurationButton: 'View Configuration',
+    openWorkspaceButton: 'Open Workspace',
+    openFolderButton: 'Open Folder',
     viewError: 'View Error'
 };
diff --git a/src/utils/utils.ts b/src/utils/utils.ts
index 5728235..83472be 100644
--- a/src/utils/utils.ts
+++ b/src/utils/utils.ts
@@ -113,3 +113,8 @@ export const showGenerateConfiguration = async (): Promise<void> => {
         await commands.executeCommand(extCommands.generate);
     }
 };
+
+export const isWorkspaceOpened = (): boolean => {
+    // The name of the workspace. undefined when no workspace has been opened.
+    return workspace.name !== undefined;
+};