Garrity made three 3-pointers and added six assists for the Hornets (11-10, 6-7 Big Sky), who came in with three one-point losses in conference play, including Monday's 62-61 heartbreaker to Northern Arizona.
Collin Chiverton had 12 points off the bench for the Eagles (6-17, 4-9).
Sacramento State led for most of the game, but Eastern Washington pulled ahead midway through the second half and led 48-44 after Thomas Reuter's 3-pointer with 8:43 to play. Sacramento State scored the next 10 points, capped by Mikh McKinney's two free throws with 4:15 left, to take the lead for good.
The Hornets led by as many as eight points in the first half before the Eagles closed the gap to 29-27 at halftime.
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point guard Melo Trimble, considered a lock to leave the program before struggling in the second half last season, has withdrawn from the NBA draft and will return for his junior season.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.