Mir, who provided short-term cover for Mitchell Santner earlier in the Blast, has picked up five wickets and scored at a strike rate above 200 in three outings for the Rapids
Worcestershire have retained the services of Usama Mir for the remainder of the T20 Blast, with the Pakistan international replacing the injured Michael Bracewell.
Allrounder Bracewell ruptured his right Achilles while batting against Yorkshire on June 9 and is expected to be on the sidelines for six to eight months.
Mir was brought into the Rapids squad at the beginning of the Blast as cover for Mitchell Santner, who was involved in the IPL.
In three outings, he picked up five wickets with an economy of 6.5 and scored 61 runs at a strike rate of 203.33.
Mir has also featured for Worcestershire in the County Championship [Warren Little/Getty Images]
He also featured in Worcestershire's County Championship clash with Sussex (June 11-14), taking two wickets.
"It was my dream to play county cricket, I realised that earlier in the competition, and I am delighted to be available for the remainder of the tournament," Mir said.
"The boys have played some good cricket, and I'm looking forward to helping them win some more games and keep challenging near the top of the table."
Paul Pridgeon, Worcestershire's cricket steering group chair, added: "Usama has signed for the remainder of the Blast and is available for the last seven (group) games.
"He really impressed during those first three games, and we are confident Usama will do a good job.
"It goes without saying that we are disappointed for Michael and hope he is back on the cricket field sooner rather than later."