Sinner and Alcaraz are widely regarded as two of the best young players on the ATP Tour at the moment. Both men entered the Umag final seeking to win their sixth title in seven singles title matches.
After taking the opening set on a tiebreak, Alcaraz was on the ascendancy. However, Sinner conceded just two games in the next two sets to dethrone the defending champion.
In the process, the 20-year-old Italian won his first title of the year, the sixth of his career and his first on clay. Meanwhile, Alcaraz came up short in a final for the second time in as many weeks after losing to another Italian, Lorenzo Musetti, in Hamburg last week.
Sinner was understandably ecstatic to win his first title of the year but also commended Alcaraz for his improving level.
"I am incredibly happy," said Sinner. "I'm coming off a tough year so far. I am very happy to finally be able to lift a trophy this year."
"Carlos, you improve every week, every tournament you play in. You've already shown amazing things this year, and I'm sure you'll play at a great level at the US Open as well. I wish you the best."
Carlos Alcaraz continues banner year, makes top-4 debut
Carlos Alcaraz has had a superb 2022 campaign despite falling in his last two title matches.
Despite losing to Sinner on Sunday and failing to defend a title for the first time, the 19-year-old has entered the top four of the ATP singles rankings. Alcaraz is now 42-7 on the season, racking up title wins in Rio de Janeiro, Miami, Barcelona and Madrid.
Last week, he entered the top five for the first time. Seven days later, only three players - Daniil Medvedev, Alexander Zverev and Rafael Nadal - are ahead of Alcaraz in the singles rankings.
The teenager has fared well at the Majors this year, reaching at least the third round in all three events. After making the third round at the Australian Open, Alcaraz played in his first Roland Garros quarterfinal (second at a Major) before reaching the second week at Wimbledon.
Following two finals on clay in as many weeks, Alcaraz will now turn his attention to the north American hardcourts. He made the US Open quarterfinals last year and will hope to do well in the tournaments leading up to Flushing Meadows.