Mahachi decided matters after Highlands veteran Surprise Moriri's 83rd-minute penalty cancelled out Knox Mutizwa's first-half opener at Princess Magogo Stadium.
Mutizwa struck in the 28th minute, converting a pass from Zimbabwean compatriot Mahachi following an interception from Sibusiso Sibeko.
Mutizwa could have made it 2-0 soon after but he struck the crossbar after being put through one-on-one with the goalkeeper.
Abafana Bes'thende consequently bolstered their tally to 30 points from 22 matches and went above Polokwane City into sixth spot on the table.
Highlands are 13th in the standings with 20 points from 22 fixtures - a point above Bloemfontein Celtic and Free State Stars, and two in front of bottom-placed Baroka.