Frosinone went into half-time 3-2 ahead of Sassuolo in a fast-paced seventh-round Serie A match, with all five goals scored within the opening 37 minutes.
Antonio Raimondo struck twice for the home side, while Giacomo Calo added the other goal to give Frosinone the advantage at the break.
Sassuolo responded through Domenico Berardi and Kristian Thorstvedt, but could not prevent the hosts from taking the lead into half-time.
The five goals came during a 28-minute spell, beginning in the ninth minute and ending with the 37th-minute strike.
Frosinone started the game ninth in the table with 10 points from their opening six matches. Sassuolo had eight points and occupied 11th place.
A victory for Frosinone would move them into the top four for 24 hours.