Marvelle Harris and Cezar Guerrero added 15 points apiece for the Bulldogs (9-9, 4-1 Mountain West Conference). Karachi Edo chipped in 10. The team hit 52 percent from the field overall and 75 percent from the line.
Fresno State went 11-2 to start and led 32-30 at halftime.
The Bulldogs extended their lead to 45-37 on a 13-7 run to kick off the second half and took it to 63-44 on a 12-5 run midway highlighted by a pair of 3-pointers by Guerrero and another by Watson. Edo finished off the Spartans (2-15, 0-5) with a pair of dunks in the final three minutes.