UK light heavyweight Buatsi secured a victory yet unimpressive debut to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a split decision in a close ten-round bout at the Manchester venue.
But Parker landed significant shots, landing some telling individual punches in a match where the approaches failed to mesh, with excessive holding disrupting the fight.
Two judges scored it 96-94 to Buatsi, with the final judge a 95-95.
"It wasn't my greatest performance but what do champions do? They win," the victor commented in the arena as he was met by disapproval from the spectators.
The British fighter bounced back after his first professional defeat - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Several boxing experts thought Parker, thirty-one, deserved the win but the British boxer suffered the second defeat of his 28-match career.
The Champion Claims Victory in Uneventful Affair
His career development has stalled in recent years through promotional disputes and long spells of inactivity.
Once tipped as the next star of UK boxing, he now stands trying to achieve expectations - possibly in what feels like a last chance - under recent support.
He began cautiously, with both competitors ready to overcommit in a calculated opening few rounds.
The challenger, whose only previous defeat came at super-middleweight against John Ryder in 2022 after damaging his hand in the contest, was making just his second fight at light heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for the favorite, who worked behind a protective stance to narrowly win the better stanzas.
The spectators' acceptance decreased because of constant clinching, with Parker slipping to the canvas various instances during clinches.
Parker closed well, but multiple periods were difficult to score. However, former world champion the boxing analyst - working with the broadcast network - had it significantly in favor for Parker, scoring for Buatsi just a single round.
Buatsi advances, but with the presence of heavy hitter David Benavidez, and Eastern European fighter Bivol leading the category, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Tribute Motivates Local Rivalry Contest
In the secondary fight, Lyndon Arthur beat Bradley Rea by split-decision in a excellent all-Manchester contest to capture the European light heavyweight championship.
The stadium grew hushed for a profoundly moving memorial before the fight as 10 bells tolled in memory of Manchester's own Hatton, who passed away aged 46 in last month.
It was the first major televised match card in the city since the passing of Hatton. As the concluding sound ended, the silence transitioned to a shout of "there's only one Ricky Hatton".
The competition during the bout reflected the sentiment. Arthur was sent to the canvas by a left hook squarely on the jaw in the initial stage, getting up unsteadily to his position on the eight count.
But the Manchester United-red equipment of the fighter soon advanced again. Across the ring, Rea - in opposing blue - was marked up quickly, noticeable damage forming under his face as the fighters landed punishing blows.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, responded in kind with powerful upward punches as the action seldom decreased over twelve rounds.
Arthur narrowly won the verdict with judges scorecards of draw, close margin and clearer margin, but the two athletes were persistent and brave, all the qualities their idol Hatton stood for.
