Juventus and Atlanta have been fined €50,000 each for crowd violence during their match at the Stadio Atleti Azzurri d'Italia in Bergamo on Wednesday.
Five people were injured as fans threw fireworks and broken bath tiles during the 1-0 win for champions Juve, causing the match to be stopped for eight minutes during the first half.
Players and officials tried to calm supporters, something that was acknowledged by Serie A's disciplinary tribunal in its report and prevented the clubs from receiving more severe punishments.
The report described the scenes as "a mutual, intense and continuous throwing of fireworks and pieces of tiles ripped from the stadium toilets".
The match was decided by Alessandro Matri's 18th-minute strike, sealing a ninth straight win for the Bianconeri, who had retained their title three days earlier.
Napoli coach Walter Mazzarri was also fined €5,000 by the tribunal for dissent during his side's 3-0 win at Bologna on the same evening as the Atalanta-Juve game.