The 1913 United States Senate election in Massachusetts was held during January 1913. Incumbent Republican Senator Winthrop Crane retired and was succeeded by Republican John Wingate Weeks.
At the time, Massachusetts elected United States senators by a majority vote of the combined houses of the Massachusetts General Court.
After winning the caucus nomination on the thirty-first ballot, Weeks's support was made unanimous by acclamation on a motion by McCall supporter Claude L. Allen. The motion was seconded by Guild supporter John L. Sherburne.