Read: Bucs' mindset is 100%
The move comes shortly after the Sea Robber defeated Kaizer Chiefs in the Carling Cup.
The club confirmed the signing on their official website:
"Sitholo joins the club from National first Division outfit Jomo Cosmos, a side he captained for a few seasons.
The 24 year old defender comes to the Mighty Buccaneers with a wealth of experience, having represented South Africa at the Under 20 and 23 levels, as well as the National Senior team, Bafana Bafana.
He is expected to join the team for training this week."
Orlando Pirates face Moroka Swallows on August 9 in the opening round of the 2014/15 PSL season.