Australian Open champion Sinner, who previously finished as runner-up in Miami in 2021 and 2023, defeated the Bulgarian 6-3 6-1.
It marks a third title of 2024 for the 22-year-old, following his successes in Melbourne and Rotterdam.
Sinner has lost just one match so far this season and will rise to a career-high second in the world rankings.
“It has been a very special week for me, I have faced different kinds of situations on the court and different opponents,” he told Sky Sports.
“I was full of energy today. I’m very happy to be number two in the world. It is just a number, for me most important is trying to execute my gameplan and I managed to do this.”
Dimitrov will rise to a world ranking of nine following his run to the final, in which he beat top seed Alcaraz and German fourth seed Alexander Zverev. It marks his first time in the top 10 since 2018.
“Even though I’m not the winner today, I feel like one,” Dimitrov said.
On Saturday, American Danielle Collins won the women’s title with a 7-5 6-3 victory over Kazakhstan’s fourth seed Elena Rybakina.
Source: BBC