The 35-year-old midfielder joined the Clever Boys as a free agent on Wednesday after parting ways with English side Sunderland AFC last week.
Pienaar, who is a childhood Pirates fan, held informal talks with the club last year before he joined Sunderland prior to the 2016/17 season.
The Johannesburg-born player recently disclosed that he would be open to signing for the Soweto giants.
Pienaar and football fans took to Twitter after Wits announced the news:
Pirate's fan's be like after Wits signed Steve Pienaar. pic.twitter.com/hgeq5NhDSy— BONGANI (@BonganiStally) July 5, 2017
I'm officially a Clever Boy— Steven Pienaar (@therealstevenpi) July 5, 2017
Pienaar is the 'biggest name' signing in the PSL after Bennie signed with Pirates but I use biggest name signing loosely here.— Philasande Sixaba (@psixaba) July 5, 2017
When someone says Thamsanqa (sp) Sangweni is better than Steven Pienaar.— Charlie Cesc Makgoba (@CWharlie4) July 5, 2017
Meaning Pirates got a better player than Bidvest Wits.