Four-time Grand Slam champion Sinner won his first title of 2026, rallying from 0-4 down in the second-set tiebreaker to seal the win against a resurgent Medvedev, winner of the title in Dubai last month, who was riding a nine-match ATP winning streak.
That included an upset semi-final triumph over Carlos Alcaraz that ended the top-ranked Spaniard's 16-match winning streak to start the season.
But Sinner, who didn't drop a set in the tournament, proved just that bit better in a match where both sets went to the tiebreakers without a break of serve.
"I kept believing and kept pushing," Sinner said of his closing burst. "I went for my shots a little more. A third set, we would have started even, so I tried my best to close it out and I am very happy.
"It was an incredible ending."
Sinner didn't face a break point in the one-hour, 55-minute contest, winning 43 of the 47 points on which he put his first serve in play.
Medvedev saved the only two break points he faced in the seventh game of the opening set, but Sinner's tiebreaker prowess proved too much.
Medvedev was up 5-4 in the first-set tiebreaker when he let a ball sail by him and it landed in.
He'd go on to save one set point, but Sinner gave himself another with a blistering forehand that the Russian couldn't handle and pocketed the set with a thundering service winner.
Medvedev looked on track to level the match when he raced to a 4-0 lead in the second-set decider - aided by Sinner's second double-fault of the match.
But Sinner roared home to join Novak Djokovic and Roger Federer as the only players to win all six of the ATP's hardcourt Masters 1000 tournaments.
Medvedev, who lost to Alcaraz in the Indian Wells finals in 2023 and 2024, missed his chance to become just the second player to beat both Alcaraz and Sinner in the same tournament.
But the former world number one underscored his return to form after a disappointing 2025 campaign and will return to the top 10 on Monday.
