In Marstons Mills, the route junctions with River Road and Main Street, a double fork in the center of the community.

After Old Famouth Road, the highway winds north along the east side of the pond, and passes Cape Cod Airport.

[2] Route 149 continues northeast along the western edge of Olde Barnstable Fairgrounds Golf Course, becoming Prospect Street after crossing through a rotary.

Route 149 runs northeast and into a partial cloverleaf interchange with US 6 (Mid-Cape Highway exit 65).

Now in West Barnstable, Route 149 becomes Meetinghouse Way and reaches a junction with Route 6A (Main Street) in downtown West Barnstable, south of Sandy Neck Beach Park.