Boshoff, who was part of the University of Johannesburg's coaching team during this year's Varsity Cup, had previously been employed by the Golden Lions Rugby Union (GLRU) as the forwards coach under Eugene Eloff between 2006 and 2009.
He takes over from Willemse whose contract was not renewed after the Leopard's poor showing. They are without a win this season with one Currie Cup fixture to play - on Friday against the Cheetahs in Phokeng - before they will be involved in the promotion/relegation play-offs.
"To return to Potchefstroom marks the completion of a circle as my career started here," said Boshoff.
"My family and I are looking forward to this new experience. I know coaching the Leopards is going to be a big challenge but I'm really looking forward to it and to have DP Swart as my assistant will be a great honour."
GLRU president Kevin de Klerk was also consulted on Boshoff's appointment as the two unions have close ties and there was a unanimous agreement that he is the right man for the job.
Boshoff played 99 matches for Western Transvaal (now the Leopards) as well as 88 matches for the Lions between 1999 and 2001.