This was confirmed on the club's website by president Patrice Motsepe.
The statement on the clubs website reads: “Johan Neeskens is a good coach whose experience and track record speaks for itself.
"He sacrificed and worked hard for the success of the club. Johan will always have a special place at Mamelodi Sundowns and I wish him the very best with his future and career.”
Sundowns also announced the appointment of Mosimane as their new head coach with immediate effect.
Motsepe said: “I am excited to welcome Pitso to Mamelodi Sundowns and am confident that he will contribute to the success and growth of the Club.
"Pitso’s first major task is to ensure that we win games and finish in a respectable position in the Premier Soccer League, taking into account the very high standards we set for ourselves.
"Our current position on the log is extremely embarrassing and we have to restore the dignity and pride of Sundowns and our supporters.”