Jimenez and Quiroz will play for the Pacific Coast League squad against the International League All-Stars in the 4 p.m. PT game, which will be broadcast live by MLB Network.
It will be the first Triple-A All-Star Game appearance for both players and the first time Tacoma has had two selections since 2009.
Jimenez, 30, is hitting .325 with 12 home runs, 49 RBIs and a .421 on-base percentage going into Thursday's game. Originally signed by the Athletics as a non-drafted free agent in 1999, he joined the Mariners' organization as a Minor League free agent prior to last season.
Quiroz, 30, is in his 14th season of pro ball and is having a breakthrough offensive year, hitting .325 with nine home runs and 28 RBIs in his first 46 games.
Quiroz played seven games in three different brief stints with the Mariners in 2006, '09 and '10, batting .261 (7-for-23) with two RBIs. He's also spent time in the Majors with the Blue Jays, Rangers and Orioles and has a career average of .208 with two home runs and 28 RBIs in 101 games.