Photos of the black and gold necklaces were accompanied by descriptions calling it "slave style" which have since been deleted, Al-Jazeera reported.
Mango blamed the screw-up on a translation error, according to Al-Jazeera.
But outraged customers tweeted that they didn't believe the excuse.
"Stop your lies! We all know that a translation error would be fixed well before products hit the shelves," one woman complained on Twitter.
Some even French actresses started an online petition with the tagline "Slavery is not fashion" that now has more than 5,000 signatures.