Evans made just one start and two substitute appearances in two-and-a-half seasons at Sundowns, and will be hoping to start afresh in Cape Town.
"Ajax Cape Town can confirm the signing of Rheece Evans on-loan from Mamelodi Sundowns," the club said in a statement. "The 26-year-old has joined the club on an 18-month loan deal.
"Evans arrived at Ikamva on Wednesday afternoon and will be available for selection for the club’s Absa Premiership meeting against Chippa United next Wednesday, with the right-back to link up with his new teammates later this week."
Evans joined Sundowns from Maritzburg United in 2014, but failed to break into the first-team.
He will add to the right-back options of coach Stanley Menzo, who has been using Erwin Isaacs in that role in recent matches.