Hollowell was claimed off waivers by the Diamondbacks on Tuesday and was optioned to Triple-A Reno.
Hollowell will enter the D-Backs' farm system after being part of the Rockies' organization since 2021. He's made 32 MLB appearances with Colorado, posting a 6.20 ERA and a 40:22 K:BB across 40.2 innings. He missed all of May with an unspecified injury but has made four appearances since being reinstated from the IL.