Colorado State dominated on defense and controlled the glass for much of the night, holding the Bulldogs to 32.7 percent shooting while winning the rebounding battle 49-29.
The Rams led by 12 at the break and scored eight of the first 10 to open the second.
Marvelle Harris led Fresno State (10-12, 5-4) with 16 points. The Bulldogs have lost three of four following a four game winning streak.
The Rams are 5-1 against Fresno State since the Bulldogs joined the Mountain West in 2012 and have not lost to the Bulldogs at home dating back to the 1994-95 season.