The result extended Sundowns' unbeaten league run at home to 31 matches, with their last defeat coming against Cape Town Spurs on the final day of the 2023/24 season. It also kept Miguel Cardoso's side level on points with the leading sides after their draw with Kaizer Chiefs at the weekend.
Sundowns controlled the contest from the outset and eventually broke the deadlock in the 21st minute. Bathusi Aubaas headed the ball back across the penalty area after Fawaaz Basadien's delivery, allowing Malibongwe Khoza to drill a finish into the net for his first goal of the campaign.
The hosts had threatened repeatedly before the opener, with Emile Lako, making his Gallants debut in goal, denying Basadien and Bennet Mokoena. Brayan Leon also went close with a header, while Marcelo Allende missed an opportunity after dispossessing Lako outside his penalty area.
Gallants offered little going forward during a one-sided opening half, although Ronwen Williams was forced into a save from Msindisi Kunene's near-post header.
Masandawana suffered a setback before the interval when Khuliso Mudau was forced off with an injury after 37 minutes. The Bafana Bafana right-back's fitness will be a concern ahead of Sunday's MTN8 semi-final first leg against Golden Arrows.
The pattern continued after the restart, with Sundowns creating further opportunities without immediately adding to their lead. Cassius Mailula was denied after being played through on goal, while Tashreeq Matthews pulled an effort wide and Themba Zwane missed a good chance after coming on as a substitute.
Mailula eventually made the difference midway through the second half. The forward created space inside the box before meeting a pass from Leon and firing into the top corner.
It was Mailula's third goal in four matches since returning to Sundowns and his second consecutive goal after scoring against Chiefs.
Gallants pushed for a way back into the contest but could not seriously trouble Williams, who saved from Katlego Otladisa late on. The Brazilians remained the more dangerous side and could have added a third through new signing Siyanda Ndlovu, but Lako made another impressive stop.
The victory leaves Gallants still searching for their first win of the season after their previous 3-1 defeat by Stellenbosch, while Sundowns can now turn their attention to their MTN8 meeting with Golden Arrows.