The win ends a title drought for the world number two that stretched back to last summer's Wimbledon and makes him the first man to defend a championship in the California desert since Novak Djokovic won three straight between 2014-2016.
In a rematch of last year's final, Alcaraz started sloppily, spraying errors around the court to fall 3-0 down but raised his level and captured the first set when his Russian opponent's forehand went wide in the tiebreak.
The Spaniard romped through the second set, raising his arms in the air and letting out a roar when Medvedev missed another forehand wide on match point.
Second seed Alcaraz smacked 23 winners to Medvedev's 11 and was especially effective against his opponent's second serves.
"I enjoy playing these kind of matches with you," Alcaraz told Medvedev during the trophy ceremony.
"Hopefully more finals ahead."
Medvedev, who briefly lost his temper with some fans in the Alcaraz-friendly crowd in the second set, was gracious in defeat.
"I'd like to congratulate Carlos," Medvedev said during the trophy ceremony.
"It's definitely your court, you like it here. Congrats to you and your team. You are doing a great job so continue this way and hopefully one day you can let me play a little bit better here," he said.
"Amazing job today and amazing job throughout the two weeks."
It was an eventful stay in the Californian desert for Alcaraz.
The two-time major champion was stung on the forehead when a swarm of bees invaded the court on Thursday, kept his number two ranking by ending Jannik Sinner's 19-match winning streak in the semis and slayed the big-serving fourth seed Medvedev in the final.
