Both clubs look destined for Serie B next season, with second-last Parma 11 points off safety with five games left and Crotone a further two points behind.
A defeat would have seen the Calabrian side mathematically demoted, but instead it grabbed its first away win of the season.
Lisandro Magallan nodded Crotone ahead after quarter of an hour in Tardini Stadium.
Brazilian Hernani pulled Parma level 15 minutes later but Simy and Adam Ounas added two more before the break for the visitors.
Gervinho and Valentini Mihaila struck twice in eight minutes after the break for Parma to level at 3-3.
But a Yordon Osorio foul on Arkadiusz Reca saw the referee point to the spot and Simy slotted in the penalty to bring his tally to 19 league goals this season, and 12 in the past nine games.
"It's a strange moment, I can't be happy at 100 percent," the 28-year-old, who is the third top scorer in Serie A behind Cristiano Ronaldo (25) and Romelu Lukaku (21), said.
"It's true that on an individual level I'm doing well, but that's not enough, what matters is the team, and we're struggling.
"We deserved this victory for a long time. Now there are five games to go, we need to finish the championship in the best way possible."