Komphela's agent Tim Sukazi has confirmed to Sowetan that the 46-year-old has signed a two-and-a-half-year contract with the Team of Choice.
"He has taken his first full training session with the team on Monday, everything is signed and sealed and Steve is very happy to be back coaching in the PSL," Sukazi said.
United had earmarked Komphela, who was surprisingly sacked by Stars last month, as their number one candidate for the vacant post after the KwaZulu-Natal side parted ways with Clinton Larsen after just nine games in charge.
Komphela's first task will be to try to restore confidence in a squad that has just a single win in their past 11 matches and currently sits one place above the relegation play-off position on goal difference.
Komphela must also rejuvenate a squad that has seven players over the age of 30 and just four 21 years old or younger. United have managed just 12 goals this season in 15 games; only bottom side Lamontville Golden Arrows have scored fewer (10).
His first match in charge will be an away match against University of Pretoria on February 5, before they host defending champions Kaizer Chiefs six days later.
Komphela is taking charge of his fifth Premier Soccer League club after spells with Manning Rangers, Ea Lla Koto, Dynamos and Platinum Stars.
He led the South African Under-20 and Under-23 teams on a full-time basis.
He was also caretaker coach of Bafana Bafana for two matches between the reigns of Pitso Mosimane and Gordon Igesund in June 2012.