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.
Jeff Goodman logs all the coaching changes following the 2015-16 college basketball season.
Indiana guard James Blackmon Jr., who averaged 15.8 points in 13 games before being injured last season, has withdrawn from the NBA draft.
Isaiah Briscoe has decided to withdraw from the NBA draft and will return to Kentucky for his sophomore season. Marcus Lee intends to transfer.