The former FC Porto and Blackburn striker has been named one of the first team coaches by the Red Devils.
McCarthy, who played for Blackburn Rovers in the Premier League, had a respectable tenure there. The South African Premier Soccer League team Amazulu was managed by the 2004 UEFA Champions League victor, and he guided them to second place two seasons prior.
The former West Ham striker will focus on aggressive play and striker positioning.
“McCarthy left his post as AmaZulu head coach in March after guiding the South African team to a record second position in the league. In 2020/21, he was named the South African Premier League’s Coach of the Season.
“The ex-forward will specialise in coaching attacking plays and positioning,” a Manchester United statement said.