Floro Flores hit his maiden goal of the new campaign last week in a precious 2-1 home win over Napoli, but this time the Italian striker required fortune to go his way.
After replacing Matteo Politano on the hour mark, Floro Flores made an immediate impact for the visitors as they fought for a late goal in what was a balanced encounter at the Renato dall'Ara stadium.
Minutes from the final whistle Bologna's defence was caught unawares by a Sassuolo counter-attack and an alert Floro Flores pounced on a deflected pass from fellow forward Karim Laribi to beat Antonio Mirante with a well-taken angled drive.
Promoted Bologna, looking for their first Serie A win since March 2014, pressed hard in the final minutes with 'keeper Mirante running up the park and coming close to making contact with his head at a corner.
But Sassuolo held on for a second consecutive win that sent the 'Neroverdi' top of the pile ahead of the rest of the weekend's fixtures.
AC Milan host Empoli in Saturday's late game while last season's runners-up Roma host champions Juventus at the Stadio Olimpico on Sunday.