Dion, 42, who was born in Charlemagne, Que., has publicly struggled with infertility.
She and her husband/manager are also the parents of a nine-year-old son, Rene Charles.
"Celine is just hoping for a healthy pregnancy. She was hoping for one baby and the news that we are having two is a double blessing," said Angelil, who was born in Montreal.
Dion's spokeswoman said the singer conceived the twins in her sixth in-vitro fertilization attempt.
She is 14 weeks pregnant and is due to find out the sex of the babies next month, Kim Jakwerth said.
In February, Dion told People Magazine that she was going to try in-vitro fertilization "until it works" after a miscarriage in August.
Later that month, she released the concert film and family documentary Celine: Through the Eyes of the World.