UK light heavyweight Buatsi earned a win yet disappointing start to his career under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's work rate seemingly secured him a majority decision in a competitive 10-round contest at the Manchester venue.
But Parker had his moments, delivering effective single shots in a fight where the approaches never quite clicked, with constant grabbing disrupting the fight.
Two judges had it 96-94 to the winner, with the third a even score.
"It wasn't my finest showing but what do champions do? They succeed," Buatsi commented in the arena as he was met by boos from the spectators.
The British fighter got back to winning after his maiden career setback - an memorable fight with his previous opponent in last winter - to secure a twentieth professional win.
Some ringside observers thought Parker, 31, should have been awarded the win but the contender suffered the second loss of his 28-bout career.
The Champion Claims Triumph in Uneventful Affair
His career development has stalled in recent times through management issues and considerable time of inactivity.
Once tipped as the rising talent of British boxing, he now is positioned trying to fulfil that early promise - maybe in what appears to be a final roll of the dice - under new promotional backing.
He began cautiously, with both competitors willing to overcommit in a cagey initial rounds.
The challenger, whose sole prior loss came at super-middleweight against his former opponent in 2022 after damaging his hand in the contest, was participating in his second bout at the higher weight class.
By the halfway stage, the underdog had kept it close, creating difficulties for Buatsi, who operated with a solid defense to narrowly win the better rounds.
The audience's tolerance wore thin because of regular grabbing, with Parker falling to the floor various instances during clinches.
The underdog ended stronger, but multiple periods were hard to judge. Although, ex-champion Carl Frampton - working with Dazn - had it particularly wide for the challenger, awarding Buatsi just a single round.
Buatsi moves on, but with the caliber of hard hitter David Benavidez, and Eastern European fighter Dmitry Bivol leading the category, the path to championship success - judging by this showing - still looks steep.
Ricky Hatton Tribute Motivates Manchester Derby Contest
In the co-main event, Arthur defeated Rea by close verdict in a excellent all-Manchester contest to capture the European light-heavyweight championship.
The arena became quiet for a extremely emotional memorial ahead of the contest as a bell ceremony sounded in honor of Manchester's own Hatton, who passed away at age 46 in recently.
It was the premier televised fight night in the urban center since the passing of Hatton. As the final chime disappeared, the silence transitioned to a chant of "there's only one Ricky Hatton".
The action inside the ropes equaled the sentiment. The eventual winner was sent to the canvas by a powerful punch flush on the face in the initial stage, standing uncertainly to his footing on the referee's count.
But the red-colored shorts of Arthur soon came forward again. Across the ring, the opponent - in rival City blue - was marked up quickly, significant bruising developing under his orbital area as the duo traded hard punches.
The challenger, twenty-seven, landed power punches but Arthur, 34, matched the intensity with stinging uppercuts as the action seldom decreased over the full distance.
Arthur edged the verdict with judges scorecards of even score, narrow lead and wider gap, but each competitor were persistent and full of heart, all the qualities their hero Hatton represented.
