The former Manchester United teammates clashed heads and exchanged angry words during the Coppa Italia quarter-final showdown on January 26.
Rossoneri striker Ibrahimovic, 39, was heard shouting: "Go do your voodoo s***, go do your voodoo s***, little d."
Lukaku, who represents Inter, then responded with: 'f*** you and your wife, you little b****'.
Sweden legend Ibrahimovic explained they had made the 'voodoo' remark in relation to a specific incident earlier in Lukaku's career when he was on Everton's books.
The 27-year-old vehemently denied Toffees owner Farhad Moshiri's claim in January 2018 that he left the Toffees after a witch doctor advised him to join Chelsea - and even threatened to sue him.
He also took to social media to issue a short statement explaining his actions and slamming all forms of racism having issued an explanation to FIGC investigators, as per Football Italia.
Ibrahimovic wrote on Twitter: 'In ZLATAN's world there is no place for RACISM. We are all the same race - we are all equal!! We are all PLAYERS some better then others.'
Belgium striker Lukaku did not accuse his former teammate of racism at the time of the incident.
Meanwhile, Paul Pogba leapt to Ibrahimovic's defence on social media in the aftermath of the clash.
He wrote on Twitter: "Zlatan… racist? He loves me too much so he's the last person I'd think of as racist! Come on, don't joke with that one!"
Zlatan… racist?