The 17-year-old invited his mother Pattie Mallette on stage with him on Saturday at the end of his Berlin concert and presented her with a cake for her 35th birthday.
But Bieber later revealed that Mallette's hair caught fire while on stage.
The Canadian singer Tweeted: 'Sick show in Berlin...brought @studiomama on stage 2 sing her happy bday but she lit her hair on fire with the candles. lol. i saved her.'
Pattie added: 'Thank you for all your b-day wishes!! All I want is your prayers. Thank u @justinbieber for the cake (& embarrassing me on stage lol.) Xo.'