Balwant Singh scored on either side of half-time to ensure a 2-0 win for the Mumbai outfit.
NorthEast were on the attack from the start and were unlucky not to have scored in the fourth minute.
Luis Alfonso nicked the ball from Achille Emana in midfield and dribbled his way into the box to get his shot away. It beat custodian Amrinder Singh, but not the upright.
The 26th minute saw the home team miss a great chance. Halicharan Narzary whipped in a pass from the left flank to which Marcinho got a toe to set up Seiminlen Doungel.
More From This Section
However, it was Mumbai City who took the lead against the run of play, and it was down to some lapse judgement from Highlanders' keeper Ravi Kumar who was covering for a suspended TP Rehenesh.
Balwant got on the other side of the defence with the ball, but the NorthEast defenders could have probably covered back. Kumar though chose to rush out of the box, and Mumbai's top scorer slotted the ball through his legs and into the goal for a 1-0 lead at the break for the visitors.
First Emana's 62nd minute shot after cutting inside was met with a smart save from Kumar. Then two minutes later, Balwant missed a glorious opportunity when Emana's free-kick found him free in the box. He could not keep his header on target though.
But the two would combine again for Mumbai's and Balwant's second. Rowllin Borges scuffed an attempted back- pass in the 68th minute, and it allowed Emana to nip in. With an on-rushing Kumar in front of him, the Cameroonian unselfishly squared it for Balwant to score into an empty net.