Tisdale, 35, took to her Instagram account to share several photos revealing the news.
In the first snapshot, the "High School Musical" alum -- wearing a white flowy dress -- is seen cradling her baby bump as she and French stood together, looking down. In the second picture, the couple lovingly looks at each other.
Tisdale left the post captionless. French also shared the news on his social media account with a photo of him standing behind Tisdale, placing his hands on her arms. Like his wife, he didn't write a caption.
The pair's celeb pals immediately commented on Tisdale's post, gushing over the baby news.
"Just the freaking cutest," Tisdale's former "High School Musical" co-star and best friend Vanessa Hudgens wrote.
"Been waiting for this!!! can't wait! Best mama & papa combo!" wrote Haylie Duff.
"So happy for you babe! You're going to be the best mama!" commented Lea Michele.
Emma Roberts, who is also expecting a baby with Garrett Hedlund, simply commented with heart-eyed emojis.
Kaley Cuoco wrote, "Omg congratulations!!!"
Tisdale and French tied the knot in 2014.