Sinitta, 45, was thrilled to reveal the happy news on Twitter last night following a Mother's Day meal with her family and friends.
Along with the news, Sinitta shared a new picture of baby Eric, in which she cradled him in her arms.
'So Macho' singer Sinitta tweeted: "Wanted you to be the first (well after my mum and children) to hear about my next Serious New Role... Drum Roll...
"At Mother's Day lunch with Mum, Magdalena, Zac, @JasonJGale @SimonCowell I was asked to be GodMother to Baby Eric !!!X ."
X Factor boss and music mogul Simon welcomed baby Eric with his partner Lauren Silverman in New York City on Valentine's Day (14 February).
Although Sinitta has now announced her official role, it was already thought that she would be taking up the role as godmother after tweeting just hours before Eric's birth: "Waiting to hear my God son has been born".
Simon and Sinitta had a brief relationship together in the 80s, but have since remained close friends. The pair were last pictured out together on 11 March, as they celebrated Cheryl Cole's X Factor return in London.
Sinitta also arrived at the premiere of the I Can't Sing musical last week, where Simon planted a giant kiss on Lauren's lips.
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