Joe Smith Jr. claimed a majority decision over Maxim Vlasov to clinch the vacant WBO light heavyweight title on Saturday.
Smith postponed his honeymoon in order to face Vlasov in the championship bout at Osage Casino in Tulsa, Oklahoma.
It proved to be a wise decision as the judges scored the fight 114-114, 115-113 and 115-112 in favour of American Smith (27-3).
Smith was forced to dig deep against Russian opponent Vlasov (45-4), landing 68 of his career-high 174 power punches over the final two rounds.
In the 11th round, Smith thought he had registered a knockdown, but the referee saw it differently, ruling he had hit Vlasov behind the head.
"It's a great feeling," Smith said as he looks ahead to an overdue honeymoon with his wife after the encounter was originally scheduled for February 13 before Vlasov tested positive for coronavirus.
"It was definitely a close, tough, tough fight. Vlasov is a great fighter and he really put on a great show tonight and toughed it out.
"In that [11th] round I hurt him, I believe he stuck his head down and I should have gotten the knockdown.
"I believe I would have gotten the stoppage. ... I landed the bigger, harder shots, but he landed a lot of punches, too. It was a great fight."
Smith added: "I want the other belts. I want the big fights out there. I believe I'm going to start unifying the belts."