Yeager made 11 of 17 shots from the field, including 6 of 11 from 3-point range, for the Titans (12-11, 5-6 Big West), who shot 65.4 percent (17 for 26) in the second half to overcome a 40-29 deficit at the break.
Kwame Vaughn had 13 points for Cal State Fullerton.
Chris Patton scored 36 points on 14 of 16 shooting for the Highlanders (5-18, 2-9).
The Titans made 8 of 14 3-point attempts in the second half. Yeager's shot from behind the arc gave Cal State Fullerton the lead for good, with 9:20 remaining.