British light-heavyweight Buatsi secured a victory yet disappointing debut to life under fresh promotional backing with a points victory over Zach Parker in Manchester.
The Olympic medal winner's work rate likely gained him a majority decision in a close 10-round fight at the boxing arena.
But Parker had his moments, delivering effective individual punches in a contest where the techniques failed to mesh, with constant grabbing marring the contest.
Two judges scored it 96-94 for to the winner, with the remaining official a 95-95.
"It wasn't my finest display but what do champions do? They win," Buatsi commented in the arena as he was greeted with boos from the spectators.
The British fighter got back to winning after his initial pro loss - an memorable fight with Callum Smith in last winter - to claim a 20th pro success.
Several boxing experts believed Parker, 31, merited the decision but the contender experienced the second loss of his 28-fight career.
Buatsi Earns Triumph in Uneventful Encounter
His career development has slowed in the past few years through contract problems and extended periods of inactivity.
Earlier forecast as the rising talent of UK boxing, he now is positioned trying to fulfil that early promise - maybe in what feels like a last chance - under fresh management.
He started carefully, with neither fighter willing to be aggressive in a cagey initial rounds.
The challenger, whose only previous defeat came at super middleweight against John Ryder in two years ago after suffering a hand injury during the bout, was competing in only his second appearance at light-heavyweight.
By the fight's midpoint, the underdog had kept it close, causing problems for the favorite, who worked behind a tight guard to barely take the cleaner stanzas.
The audience's tolerance decreased because of frequent holding, with Parker falling to the floor several times during clinches.
The underdog ended stronger, but multiple periods were difficult to score. Although, former world champion Carl Frampton - working with the broadcast network - had it significantly in favor for Parker, awarding Buatsi just a single round.
Buatsi moves on, but with the likes of power puncher David Benavidez, and Eastern European fighter Dmitry Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Memorial Inspires All-Manchester Fight
In the co-main event, Arthur overcame Rea by divided decision in a terrific Manchester vs Manchester contest to capture the continental belt.
The stadium became quiet for a profoundly moving tribute prior to the bout as ten bells tolled in remembrance of Manchester's own Hatton, who succumbed aged 46 in recently.
It was the initial significant broadcast boxing event in the urban center since Hatton's passing. As the last bell ended, the stillness transitioned to a chant of "there's only one Ricky Hatton".
The fighting within the ring matched the sentiment. Arthur was knocked down by a left hook flush on the jaw in the second round, getting up unsteadily to his feet on the referee's count.
But the traditional red attire of Arthur soon came forward again. Across the ring, Rea - in rival City blue - was damaged early, heavy swelling appearing under his orbital area as the fighters exchanged hard punches.
Rea, 27, connected with strong blows but the champion, thirty-four, fought fire with fire with powerful upward punches as the intensity hardly diminished over the full distance.
The victor barely secured the decision with scoring tallies of even score, 115-113 and 115-112, but each competitor were determined and courageous, all the qualities their inspiration Hatton embodied.
