The Sea Robbers went down to Dimitri Bissik's 72nd minute strike in Dolisie.
The result sees Leopards join Bucs and Al Ahly at the summit, with the latter having a chance to move clear if they defeat Zamalek on Sunday.
In a goalless opening period, Pirates striker Lennox Bacela had a great chance to score but the ex-Bloemfontein Celtic man volleyed off target off a cross from Patrick Phungwayo.
Earlier, Daine Klate drilled a free-kick straight at Leopards goalkeeper Lawrence Ngome, while at the other end Bhebey Ndey shot wide, with Buccaneers keeper Senzo Meyiwa also making a smart stop to keep his team in it at one stage.
Leopards showed intent after the restart, and eventually got their reward when Bissik fired the ball past a back-tracking Meyiwa after the gloveman - who was making his 100th Bucs outing - failed to gather a corner.
Bafana Bafana winger Klate threatened with a late free-kick, which went narrowly wide, but the hosts held firm to claim the three points.
Orlando Pirates starting XI: Meyiwa, Lekgwathi, Mahamutsa, Phungwayo, Sangweni, Masalesa, Manyisa, Myeni, Klate, Mbuyane, Bacela.
Leopards starting XI: Ngomé, Nzamba, Moubhio, Miangounina, Bissiki, Lakolo, Gandzé, Niemba, Ntela, Mouzita, Ndey.