Pitcher Leo Rosales was activated from the 60-day disabled list and fellow hurler Carlos Rosa was promoted from Triple-A Reno along with first baseman Brandon Allen and infielder Tony Abreu.
"Intermittently we'll be adding more guys," interim GM Jerry Dipoto said. "Our Double-A Mobile club is going to the playoffs and has a chance to win the Southern League title so we want to give them every opportunity to do that."
Rosales was placed on the disabled list April 28 and underwent surgery to repair a stress fracture in his right foot.
"It's been a long time coming," Rosales said of getting back to the active roster. "But it feels great. I'm going to try and do my best this month ... and finish strong."
Rosa, who was acquired May 1 from the Royals, appeared in 15 games earlier this year with the D-backs and was 0-2 with a 6.75 ERA.
Abreu was with the D-backs until being optioned to Reno on Aug. 4 as the team tried to get him some consistent at-bats after getting limited playing time at the big league level.
"The reason we sent him down was looking at his development," D-backs manager Kirk Gibson said.
Abreu made the most of his increased playing time going 33-for-94 (.351).
Allen was acquired from the White Sox last year and hit .202 in 104 at-bats.