England manager Gareth Southgate kept only Dominic Calvert-Lewin and Kieran Tripper from the side that thrashed Wales, as he brought back the regulars but Raheem Sterling was ruled out while Harry Kane started on the bench with fitness concerns.
Meanwhile, the Red Devils also welcomed back their big guns after they were rested in the draw against Ivory Coast, with Kevin De Bruyne captaining the side but first-choice shot-stopper Thibaut Coutois was out injured.
Yannick Carrasco thought he had got the opener for the visitors in the tenth minute after thumping a low strike past goalkeeper Jordan Pickford from Thomas Meunier's cut-back but the goal was ruled out for offside.
However, Romelu Lukaku fired the Red Devils ahead five minutes later by sending Pickford the wrong way from the penalty spot after Eric Dier brought him down inside the box with a sliding challenge.
Marcus Rashford levelled matters for the Three Lions five minutes before the break with a powerful penalty towards the top corner after Meunier pulled Jordan Henderson down inside the box, in an off-the-ball incident from a corner situation.
The hosts were positive coming from the break and they went 2-1 up in the 65th minute after Mount's curling shot took a deflection off Toby Alderweireld's raised foot, looped over goalkeeper Simon Mignolet and dipped into the top corner.
Carrasco should have brought Belgium back into the game with 20 minutes remaining after he went through from De Bruyne's clever through ball but he guided his first-time shot just wide of the bottom post.
Second-half substitute Kane had a good chance to put the game beyond the Red Devils in the last nine minutes with a free header from a corner but he scuffed his effort wide and Rashford also missed a good chance minutes later but it did not matter as the hosts held on to grab top spot by just one point over Belgium in League A, Group 2.