After his dogfight with fellow Italian Matteo Berrettini ended shortly before the 11 p.m. local curfew on Wednesday, he wasted little time under the roof on Centre Court.
A backhand rocket earned Sinner the early break and set the tone for the opening set, which he sealed in 21 minutes dropping only one late game.
Kecmanovic came into the match with an uphill task having never beaten Sinner in three previous meetings and he did well to delay the inevitable in a tight second set.
He was soon staring down the barrel, however, as Australian Open champion Sinner broke for 5-4 before blasting three aces en route to tightening his vice-like grip with a two-set lead.
The winners continued to flow from Sinner's racket as the lanky top seed raced to another huge lead in the third set and Kecmanovic put himself out of his misery with an error.