Sinner, the Australian Open winner who finished runner-up in Miami in 2021 and 2023, overcame the Bulgarian 6-3 6-1.
The 22-year-old now has three titles in 2024, following wins in Melbourne and Rotterdam.
Sinner has only lost one match this season and is on track to finish second in the global rankings, a career high.
“It has been a very special week for me, I have faced different kinds of situations on the court and different opponents,” he stated in an interview with Sky Sports.
“I felt energised today. I’m overjoyed to be number two in the world. It’s only a number; what matters most to me is executing my game plan, which I did.
Sinner becomes the first Italian to enter the top two since the ATP rankings were first published in 1973, defeating Spain’s Carlos Alcaraz.
After the first three games of the opening set raced by, with Dimitrov serving cleanly and Sinner dropping only one point on service, the 32-year-old Bulgarian, playing in his first Miami final, had the first chance to go ahead.
But Sinner saved Dimitrov’s break point, and the younger man took over from there, breaking serve in the very next game and forcing the world number 12 to save two more break points before sealing the set with a brilliant backhand down the line.
Sinner maintained his dominance in the second set, conceding only three games on service before sealing the victory on his first championship point with another backhand winner.
Dimitrov will move up to world number nine after reaching the final, where he defeated top seed Alcaraz and German fourth seed Alexander Zverev. It is his first appearance in the top ten since 2018.
“Even though I’m not the winner today, I feel like one,” Dimitrov remarked.
Danielle Collins, an American, won the women’s title on Saturday, defeating Kazakhstan’s fourth seed Elena Rybakina 7-5 6-3.
