Early career Serghei Spivac made his MMA debut in September 2014 with the Ukrainian promotion Real Fight Promotion, at 19 years old. He faced Andrey Serebrianikov as his first opponent. He won the fight in the last minute of the first round, by way of TKO. His second fight was with the Ukrainian-based World Warriors Fighting Championships, at WWFC Ukraine Selection 1, where he faced Evgeniy Bova in the main event. Spivac won the fight in the first round by way of a kimura. His second fight with World Warriors Fighting Championships was during WWFC: Ukraine Selection 4, in the main event. His opponent was Yuri Gorbenko, whom he defeated in the first round through an armbar. Spivac would than fight against Dimitriy Mikutsa, under the N1 Pro organization. Spivac submitted Mikutsa through an armbar during the last minute of the second round. Under the banner of Eagles Fighting Championship, Spivac faced Artem Cherkov. Spivac would beat him in the first round, by way of a head kick. After a year-long layoff, Spivac would return to the World Warriors Fighting Championships. His first opponent was Luke Morton, whom he beat by KO. In his next fight Spivac fought against the MMA veteran
Travis Fulton for the vacant WWFC Heavyweight Championship, a fight which he won in the first round by a rear naked choke. He would defend the title 10 months later against the Croatian fighter Ivo Cuk, winning the bout in the first round by TKO. His last fight with WWFC was his last title defense, five months after his fight with Cuk, against Tony Lopez. He defeated Lopez by a neck crank in the last minute of the first round.
Ultimate Fighting Championship Spivac made his UFC debut during
UFC Fight Night 151, at 23 years old, against
Walt Harris, replacing
Alexey Oleynik. He suffered the first professional loss of his career. Harris pushed Serghei up to the cage, dazed him with a left straight and dropped him to the floor with a barrage of knees. After a series of grounded strikes, the referee awarded Harris a win, after 50 seconds, by way of TKO. Five months later, Spivac fought against
Tai Tuivasa at
UFC 243. Spivac would begin the fight being cautious of Tuivasa's power. Spivac was dropped once in the first round by a leg kick. Spivac then began catching Tuivasa's leg kicks and would take the Australian down. Whenever the Australian would return to his feet, Spivac would pursue takedowns. The fight ended in the fourth minute of the second round, Spivac took Tuivasa down for the 7th time in the fight. He was able to obtain the mount and after several hard punches and elbows he was able to obtain an arm triangle choke, awarding him his first UFC win. Spivac faced
Marcin Tybura on February 29, 2020, at
UFC Fight Night 169. He lost the fight via unanimous decision. Spivac was expected to face
Carlos Felipe on May 9, 2020, at
then UFC 250. However, on April 9,
Dana White, the president of UFC announced that this event was postponed to a future date Eventually the bout was scheduled on July 19, 2020, at
UFC Fight Night 172. He won the fight via majority decision. Spivac was expected to face
Tom Aspinall on October 11, 2020 at
UFC Fight Night 179. However Spivac withdrew from the bout for undisclosed reason and he was replaced by promotional newcomer
Alan Baudot. Spivac was scheduled to face
Jared Vanderaa on December 12, 2020, at
UFC 256 However, Vanderaa tested positive for COVID-19 during fight week and had to be pulled. The pair eventually met on February 20, 2021, at
UFC Fight Night 185. Spivac won the fight via technical knockout in round two. Spivac faced
Alexey Oleynik on June 19, 2021, at
UFC on ESPN 25. He won the bout via unanimous decision. Spivac faced
Tom Aspinall, replacing
Sergei Pavlovich, on September 4, 2021, at
UFC Fight Night 191. He lost the fight via technical knockout in round one. Spivac was scheduled to face
Greg Hardy, replacing
Aleksei Oleinik, on January 22, 2022, at
UFC 270. However, just a week before the event Hardy withdrew due to a finger injury and the bout was removed from the event. The pair was moved to
UFC 272. Spivac won the fight via technical knockout in round one. Spivac faced
Augusto Sakai on August 6, 2022, at
UFC on ESPN 40. He won the fight via technical knockout in round two. Spivac was expected to face
Derrick Lewis in the main event of
UFC Fight Night 215 on November 19, 2022. However, Lewis was forced to pull out of the event due to non-COVID, non-weight cutting illness and the bout was cancelled. The pair was rescheduled for
UFC Fight Night 218 on February 4, 2023. Spivac won the fight via an arm-triangle choke in round one. This win earned Spivac his first
Performance of the Night bonus award. Spivac faced
Ciryl Gane on September 2, 2023, at
UFC Fight Night 226. He lost the fight via technical knockout in the second round. Spivac faced
Marcin Tybura in a rematch on August 10, 2024, at
UFC on ESPN 61. He won the fight via an armbar submission in the first round. This fight earned him another
Performance of the Night award. Spivac faced
Jailton Almeida on January 18, 2025, at
UFC 311. He lost the fight by technical knockout at the end of the first round. Spivac was scheduled to face
Shamil Gaziev on May 17, 2025, at
UFC Fight Night 256. However, for unknown reasons, their bout was moved to
UFC 316 on June 7, 2025. In turn, Gaziev pulled out due to a broken finger and was replaced by
Waldo Cortes-Acosta. He lost the bout via unanimous decision. 10 out of 13 media outlets scored the bout for Spivac. The bout between Spivac and Gaziev has been re-scheduled to take place on November 22, 2025, at
UFC Fight Night 265. However, Spivac withdrew from the bout for unknown reasons and was replaced by
Waldo Cortes-Acosta. Spivac was scheduled to face
Ante Delija on February 1, 2026 at
UFC 325. However, the bout was moved to February 21, 2026 at
UFC Fight Night 267 for unknown reasons. Spivac won the fight by unanimous decision. ==Personal life==