The incident occurred at full time in Sunday's top-flight clash at Lecce's Stadio Via del mare - which Hellas Verona won 1-0 - where D'Aversa walked up to Henry and headbutted him in the chin.
Both the 48-year-old and Verona forward Henry received red cards, and the former was condemned by Lecce, who said: "US Lecce, with reference to the episode involving the coach D'Aversa and the Verona player Henry, while evaluating the situation of general nervousness at the end of the match, firmly condemns the gesture of its coach as it is contrary to the principles and values of sport."
D'Aversa admitted that his actions were "inexcusable" in an interview to Sky Italia and claimed that he had originally tried to prevent his own players from being sent off due to Verona's "provoking".
"I went on to the pitch to try and stop my players being sent off as Verona were provoking us a lot in the final moments of the match and after the final whistle," the former Sampdoria boss said.
"It wasn't a nice thing to do, I know that. It's inexcusable and I've been to explain my actions to Verona. I didn't come on the pitch to do that."
Following D'Aversa's disgraceful actions, Lecce have unsurprisingly parted company with the manager, who leaves with a record of just six wins from 30 games in charge since being hired last summer.
"After the events that occurred at the end of the Lecce - Verona match, US Lecce announces that it has relieved coach D'Aversa of his duties," Lecce said in a statement. "Thanks go to the coach and his staff for the work done."
As well as winning just 20% of his games in charge, D'Aversa - who previously took charge of Parma, Sampdoria and Virtus Lanciano - oversaw 10 draws and 14 defeats at the Lecce helm.
Sunday's loss to Hellas Verona, who prevailed thanks to a Michael Folorunsho winner, was Lecce's fourth defeat from five games and leaves the Salentini 15th in the Serie A table, just one point clear of the relegation zone.
Lecce, who were promoted back to the top flight in 2022 and finished 16th last season, are next in action away to Salernitana on Saturday evening.