The 38-year-old star, who welcomed daughter Olive in September 2012, was spotted with tiny baby bump over the weekend and finally came out with the truth on Monday, reported Us magazine.
Drew Barrymore's second pregnancy didn't come as a surprise as the actress had made it clear that she wanted another kid right away.
"I was an only child, and it was lonely. Some people love it and thrive on the independence, but I want my kids to have other kids around," she had said.
Barrymore began dating Kopelman, the son of former Chanel CEO Arie Kopelman, in early 2011 and the couple announced their engagement in January 2012. They tied the knot on June 2, 2012 in Montecito, California.