Céline, 51, shared the birthday tribute message in both French and English.
“Double the laughter and double the love,” she wrote.
“Happy 9th Birthday, Nelson and Eddy! I’m so very proud of my boys. I love you! — Mom xx … ”
As well as her twins, Céline is also mum to 18-year-old René-Charles.
Her boys' father, René Angélil, was the singer's manager as well as her husband, but sadly passed away in 2016, aged 73.
Last year, Celine revealed that she was feeling fragile after learning to live without her beloved husband, René.
"Even after he's gone, I still talk to him," Celine revealed in an intimate interview with Stellar magazine.
Since René's death, Céline has worried fans who are concerned about her relationship with Pepe Munoz - her creative director and longtime best friend.
According to reports, Pepe has been too controlling of the powerhouse singer and forced her to listen to everything he says.
However, Celine responded to the accusations in August through a post on Instagram featuring a letter written by her real inner circle:
"Dear Pepe, as the real members of Celine's 'inner circle', we are saddened and disappointed by an untruthful story that surfaced in the media on Monday, quoting multiple sources who claim they are part of the inner circle and that you have too much influence over Celine, and that you are isolating her. These 'sources' have nothing better to do than to spread untrue gossip. Don't let it get you down… and keep up the great work. We love you! Dave, Dee, Denis, Lina, Michel, Naomi, Suzanne, Sydney, Sylvie, Yves."