Mother Louise Wilkinson bought the children's toys as a treat for children Tia, Monet and Shannon.
But when they were unpacked and switched on, the children swear blind that one of the two bundles of fluff uttered a naughty word.
The toys are designed to pick up words that are spoken to them, but Louise insists she hadn't sworn at them and they were newly out of the packet after being bought from Argos in Oswestry.
The 42-year-old mother, from Llanfyllin, has now taken the toys from her children as a precaution.
She said: "I was in shock as I couldn't believe what I was hearing."
"It's only the one Furby that swears, but we have had to take all three from the children otherwise it wouldn't be fair and they are so upset."
It is not the first time Furbies have been caught swearing. The internet includes a number of sites in which tips are given on how to teach the toys naughty words.
Tens of millions of Furbies have been sold since they were launched in 1998, when they were the biggest selling toy of the year. The toys are capable of talking in 24 languages.