The former Spice Girl - who has been Down Under acting as a judge on `The X Factor (Australia)` - was talking to her 12-year-old daughter Phoenix when the winged insect flew into her mouth.
She wrote on her twitter page: "Ahhh gonna take a piece of OZ with me, I swallowed a Sydney fly last week, don`t laugh I actually did!!
"ok this is the first time it`s ever happened, i was taking to my daughter Phoenix and the fly just flew into my mouth hahah gotta laugh - nooooo maggots! (sic)"
Mel - who also has four-year-old daughter Angel with former boyfriend Eddie Murphy and newborn girl Madison with current husband Stephen Belafonte - is now going to implement a closed mouth policy whenever she is around flying bugs from now on.
She added in other tweets: "when the fly went into my mouth i chocked and cried and my daughter Phoeinx could not stop laughing!!
"for now on when i see a fly i will not bloody talk, didn`t no my mouth opened that wide when i spoke, i feel like it`s still in my tummy ewwww (sic)"
Mel is set to return to her home in Los Angeles now `The X Factor (Australia)` is finished but she will be continuing in her role as an ambassador for Australian weight loss company Jenny Craig, however, it is not yet known whether she will be returning to the TV talent show next year.