The gorgeous actress, who already has a one-year-old daughter Olive, confirmed the exciting news on Tuesday.
"Last time I never commented on it and people just stalked me the entire time," Drew told PEOPLE. "So yes, it's happening, it's true. I tried to keep it a secret for as long as possible."
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Drew has previously spoken about her desire to expand her family with art consultant husband Will Kopelman, and give baby Olive a younger sibling.
"Will is just thrilled — we both are," said Drew. "We just wanted so badly for Olive to have a sibling. In some ways, it's really for her. So congratulations, Olive!"
The doting mother gave birth to her first child in September 2012. "She's a sweet person, which is all I care about," said Drew. "I am obsessed with nice. That's the most important thing."
The 38-year-old actress recalled the joyous moment when she found out she was pregnant again.
"I was overjoyed," said Drew. "It always feels so surreal, it's incredible. [I'm feeling] incredible, that, 'Here we go again' feeling. And blessed. Blessed."
Speculation that the mother-of-one was pregnant started when Drew was spotted wearing loose clothing. The blossoming actress seemed to be hiding a baby bump beneath a floor-length gown when she attended the LACMA Art+Film gala event at the weekend.