The baby girl was born first, weighing in at five pounds, three ounces (2.4 kilograms), while her brother followed, weighing five pounds, six ounces (2.5 kilograms).
Soon after news of the birth broke, the couple's famous friends flooded Twitter.com with congratulatory messages.
Hip-hop star Minaj wrote, "Congratulations Mariah & Nick! The twins have finally landed on earth! Yaaayyyyy!," while Milano sent the couple a message saying, "Congrats!"
Carey's One Sweet Day collaborators, Boyz II Men, wrote, "Just got the news! Congrats Mr and Mrs Cannon on ur (your) twin babies!! Look forward to sleepless nights for the next few weeks..." while music producers Jermaine Dupri and Rodney Jerkins also sent their best wishes.