The 'Touch My Body' singer and her husband welcomed a son and a daughter together on Saturday, which also happened to be the third anniversary of their wedding.
As the couple got to know the new additions, Hall Pass actress Milano was quick to spread the happy news on Twitter, prompting more celebrities to send their well-wishes.
'Moment 4 Life' singer Minaj tweeted to Carey: "Congratulations Mariah & Nick! The twins have finally landed on earth! Yaaayyyyy!"
R&B group Boyz II Men, who collaborated with Carey on 1995 hit 'One Sweet Day', later added: "Just got the news! Congrats Mr and Mrs Cannon on ur (your) twin babies!! Look forward to sleepless nights for the next few weeks..."
Music producers Jermaine Dupri and Rodney Jerkins were also amongst the mass of Twitter users congratulating the couple.
Cannon, who previously described the birth as "the most incredible anniversary gift", returned to the social networking site this evening to declare: "I'm in the happiest place I've ever been in my life. I never had more amazing things happening. I am humbled by God's Favour!!"