Geography South Dennis is located on Cape Cod, in the center of the town of Dennis at . It is bordered by the town of Brewster to the northeast, the town of Harwich to the southeast, the CDPs of Dennis Port to the south and West Dennis to the southwest, the town of Yarmouth to the west, and the CDPs of Dennis and East Dennis to the north.
Geography South Dennis is located on Cape Cod, in the center of the town of Dennis at  It is bordered by the town of Brewster to the northeast, the town of Harwich to the southeast, the CDPs of Dennis Port to the south and West Dennis to the southwest, the town of Yarmouth to the west, and the CDPs of Dennis and East Dennis to the north.