The former Chelsea boss, 57, has left the Serbian champions after a short spell citing "personal reasons" for his exit from the club.
The Israeli boss led the Serbian giants to a fifth consecutive domestic title, but he came under heavy criticism from many fans for losing all three derby games against archrival Red Star Belgrade and failing to secure the title at an earlier in the season despite benefiting from a 10-point cushion atop the rankings back in January when he took over from Aleksandar Stanojevic.
In a press conference held at the Partizan training ground, Grant claimed he was leaving the club for "personal reasons".
"My plan was to stay longer, but in life some unplanned things always occur. I will always be there to assist Partizan," Grant said before confirming he would attend the Champions' League final at the Allianz Arena this weekend where his former Chelsea players face Bayern Munich.
The Partizan board was quick to appoint former Kaizer Chiefs coach Vladimir Vermezovic as his replacement, while Grant took his players to a farewell dinner.
Recent speculation of Grant taking over at Bolton were quelled by the Wanderers relegation from the Premier League, leaving his future destination unknown.