On-loan striker Tokelo Rantie netted an early goal to put Bucs in the lead and they never relinquished their advantage, holding out for a narrow but deserved victory.
The home side almost opened the as early as the first minute under fortunate circumstances when a clearance from Pirates goalkeeper Senzo Meyiwa struck Goodman Dlamini on the face but the ball went just wide of the upright.
However, the visitors went ahead five minutes later when a long ball from the back was headed down by Benni McCarthy; then a poor clearance by Thamsanqa Teyise allowed Rantie to finish with a powerful shot from the centre of the penalty area.
Usuthu went forward in search of the equalizer and came close to getting one in the eighth minute when Marc Van Heerden found himself with space to shoot outside the penalty area but Meyiwa did well to push his low shot around the post.
In the 18th minute Rantie came close to grabbing his second goal of the game when he latched onto another flick from McCarthy before racing towards the right side of the box, but his powerful low drive was pushed wide by Mbongeni Mzimela.
Rantie continued to trouble the Usuthu defence and in the 26th minute he collected a clearance from Thabo Matlaba on the left flank and cut inside his marker before firing a low shot which went just wide of the near post.
Ayanda Dlamini had a quiet first half by his standards but he did make his presence felt in the 37th minute.
The Nongoma-born striker met a throw-in from Tsweu Mokoro with a brilliant turn into the box before unleashing a powerful shot which was tipped over the crossbar by Meyiwa to keep his side ahead going into the break.
The home side then fired the first shot in anger five minutes after the break when Tangeni Shipahu ran free on the right but his shot was blocked by Meyiwa at the near post.
The Buccaneers threatened again in the 64th minute when Rantie collected the ball in the middle of the park before playing a neat one-two with McCarthy on the edge of the area, but his shot went wide of goal.
Neither of the two sides managed to create clear chances in the closing stages of the match and Pirates were able to hold on for maximum points.