Matteo Politano and Lorenzo Pellegrini gave the home side an early two-goal advantage. Rodrigo Palacio brought one back before Politano completed his brace just before the interval. Jeison Murillo was dismissed part way through the second half.
The away side thought they had taken the lead after five minutes when Stevan Jovetic tucked the ball away, but the play was correctly ruled back for offside.
Inter fell asleep after the passage of play and conceded less than a minute later. Gregoire Defrel found Politano just outside the box whose effort deflected off the inside leg of Juan Jesus and past a helpless Juan Pablo Carrizo.
Sassuolo sliced through the Inter backline again in the 25th minute and doubled their lead. Former Inter youth player Alfred Duncan played ball across face of goal for Pellegrini to tap into the open net. Nerazzurri defenders were upset over a hint of a foul and possible offside.
In the 32nd minute a Francesco Magnanelli error sent Palacio through on goal and the Argentine’s cool left-footed finish beat Consigli at the far post.
Five minutes later, Inter were caught napping and the two-goal advantage was restored. Politano scored his second of the match with an accurate header from a Marcello Gazzola cross, concluding a frenetic first half.
A second Inter goal was ruled out for offside a minute after the interval, though it seemed that Eder was the guilty party, not goalscorer Danilo D’Ambrosio.
The Nerazzurri were reduced to ten men when Murillo was shown a second yellow card for dissent, perhaps harshly.
The victory solidifies sixth place for Sassuolo who will now hope that Juventus can defeat AC Milan in the Coppa Italia final, which would see the Neroverdi through to the qualifying phase of the Europa league for the first time in club history.
Meanwhile, the result does nothing for Inter who were already assured fourth place, and it definitely showed in another lethargic performance.