Rourke sent 29-year-old Pasadena native Elliot Seymour to the canvas twice in the second round before the referee stopped the fight.
The bout at a Moscow concert hall was Rourke's first fight in 20 years. He took a break from acting in the early 1990s, finishing a three-year pro boxing career with six wins and two draws.
He hinted that the return to the ring has helped him cope with unspecified personal issues.
"I've got some things going on in my life so that (boxing has) sort of saved me from myself," Rourke told Russian TV. "And for a man like me, it's better to live in fear than go on in shame."
He has said he plans to hold another four fights in Russia.
Rourke prepared in a dressing room in front of a shrine featuring candles, images of saints, and photographs of his dogs. Rourke said he had been in mourning for his recently-deceased Chihuahua.
He took to the ring in a Stetson hat, a red-and-gold robe and shiny gold gloves, repeatedly crossing himself.
Rourke, who had said he lost 35 lbs (16 kilograms) to prepare to the fight, was much thinner than in his best-known cinematic fighting persona, when he bulked up to play the title character in 2008's "The Wrestler." His shorts bore his ring nickname from the 1990s, Marielito, with a Spanish-language message reading "always handsome."
The fight was held at a pedestrian pace, with both Rourke and Seymour frequently backing away from one another and letting down their guard.
Several of Rourke's punches appeared illegal. His final punch struck the stumbling Seymour on the buttocks and the 29-year-old went down to all fours until the referee stopped the contest. The Russian crowd chanted "Misha," a short form of the Russian name Mikhail, in Rourke's honour.
Seymour, a former California Golden Gloves champion with a 1-9 pro record, did not land any significant blows on Rourke, whose previous boxing career left him with injuries that he has previously said necessitated extensive plastic surgery to his face.
Following the fight, the crowd was treated to a concert by Grigory Leps, a Russian rock singer who has been barred from entering the United States due to alleged mafia connections.
On the undercard, Olympic light-heavyweight champion Egor Mekhontsev continued his unbeaten start to his professional career, moving to a 7-0 record with a win over Ugandan fighter Joey Vegas.
Russia's Eduard Troyanovsky knocked out Jose Agustin Feria of Colombia in the first round for the WBA intercontinental lightweight title, moving to a 20-0 record.