diff --git a/src/core/dependency-transformer.ts b/src/core/dependency-transformer.ts
index 3cdb904..b3eb1fd 100644
--- a/src/core/dependency-transformer.ts
+++ b/src/core/dependency-transformer.ts
@@ -26,11 +26,13 @@ export class DependencyTransformer {
       return this.versionMapCache;
     }
 
-    // Find workspace root (look for pnpm-workspace.yaml)
-    const workspaceRoot = await this.findWorkspaceRoot(rootPath);
+    // Find workspace root (pnpm-workspace.yaml or package.json with workspaces)
+    const { root: workspaceRoot, type: workspaceType } = await this.findWorkspaceRoot(rootPath);
 
-    // Parse pnpm-workspace.yaml to get package patterns
-    const patterns = await this.parseWorkspaceFile(workspaceRoot);
+    // Get package patterns based on workspace type
+    const patterns = workspaceType === 'pnpm'
+      ? await this.parsePnpmWorkspaceFile(workspaceRoot)
+      : await this.parseNpmWorkspaceFile(workspaceRoot);
 
     // Glob all matching packages
     const packagePaths = await glob(patterns, {
@@ -63,39 +65,56 @@ export class DependencyTransformer {
   }
 
   /**
-   * Find workspace root by looking for pnpm-workspace.yaml
+   * Find workspace root by looking for pnpm-workspace.yaml or package.json with workspaces
+   * Supports both pnpm and npm/bun workspace patterns
    */
-  private async findWorkspaceRoot(startPath: string): Promise<string> {
+  private async findWorkspaceRoot(startPath: string): Promise<{ root: string; type: 'pnpm' | 'npm' }> {
     let currentPath = startPath;
     const maxDepth = 10;
     let depth = 0;
 
     while (depth < maxDepth) {
-      const workspaceFile = join(currentPath, 'pnpm-workspace.yaml');
+      // Check for pnpm-workspace.yaml first (pnpm style)
+      const pnpmWorkspaceFile = join(currentPath, 'pnpm-workspace.yaml');
       try {
-        await readFile(workspaceFile, 'utf-8');
-        return currentPath;
+        await readFile(pnpmWorkspaceFile, 'utf-8');
+        return { root: currentPath, type: 'pnpm' };
       } catch {
-        const parentPath = dirname(currentPath);
-        if (parentPath === currentPath) {
-          // Reached filesystem root
-          break;
-        }
-        currentPath = parentPath;
-        depth++;
+        // Not found, continue
       }
+
+      // Check for package.json with workspaces field (npm/bun style)
+      const packageJsonPath = join(currentPath, 'package.json');
+      try {
+        const content = await readFile(packageJsonPath, 'utf-8');
+        const pkg = JSON.parse(content);
+        if (pkg.workspaces && Array.isArray(pkg.workspaces)) {
+          return { root: currentPath, type: 'npm' };
+        }
+      } catch {
+        // Not found or invalid, continue
+      }
+
+      const parentPath = dirname(currentPath);
+      if (parentPath === currentPath) {
+        // Reached filesystem root
+        break;
+      }
+      currentPath = parentPath;
+      depth++;
     }
 
     throw new DevPublishError(
-      'Could not find workspace root (pnpm-workspace.yaml). ' +
-        'Make sure you are inside a pnpm workspace.'
+      'Could not find workspace root. ' +
+        'Make sure you are inside a pnpm workspace (pnpm-workspace.yaml) ' +
+        'or npm/bun workspace (package.json with workspaces field).'
     );
   }
 
   /**
    * Parse pnpm-workspace.yaml to extract package patterns
    */
-  private async parseWorkspaceFile(workspaceRoot: string): Promise<string[]> {
+  private async parsePnpmWorkspaceFile(workspaceRoot: string): Promise<string[]> {
     const workspaceFile = join(workspaceRoot, 'pnpm-workspace.yaml');
     const content = await readFile(workspaceFile, 'utf-8');
     const yaml = YAML.parse(content);
@@ -109,6 +128,23 @@ export class DependencyTransformer {
     return yaml.packages;
   }
 
+  /**
+   * Parse package.json workspaces field to extract package patterns (npm/bun style)
+   */
+  private async parseNpmWorkspaceFile(workspaceRoot: string): Promise<string[]> {
+    const packageJsonPath = join(workspaceRoot, 'package.json');
+    const content = await readFile(packageJsonPath, 'utf-8');
+    const pkg = JSON.parse(content);
+
+    if (!pkg.workspaces || !Array.isArray(pkg.workspaces)) {
+      throw new DevPublishError(
+        'Invalid package.json: missing or invalid "workspaces" field'
+      );
+    }
+
+    return pkg.workspaces;
+  }
+
   /**
    * Transform workspace:* dependencies to actual versions
    * @param devTimestamp Optional dev timestamp to create dev versions for workspace deps