The Eagles (4-2) led 39-27 at halftime, then basically took charge in the second half. They led by as many as 22 points halfway through the second half.
UMass (6-2) never came closer than nine points the rest of the way.
Stephane Lasma had a career-high 24 points for UMass. Rashaun Freeman added 16.
The teams stayed close for the first 10 minutes before Boston College began pulling away. Three-pointers by Marquez Haynes, Dudley and Marshall moved the Eagles in front 39-25.
Marshall had 10 of his points in the first half.