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.
Maryland point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.
Louisville's Chinanu Onuaku, who recently underwent a medical procedure to correct a heart rhythm issue detected during the combine, will keep his name in the NBA draft pool.
Andrew White III will return to the Nebraska men's basketball team next season after removing his name from the NBA draft.