The newborn joins his 2-year-old sister, Viola.
Hilty and Gallagher -- who married in November 2013 -- found a clever way of announcing that they were expecting another baby. Last September, the Smash star posted a photo of herself surrounded by desserts while wearing a T-shirt that read: "Eating for two."
WATCH: Tori Spelling and Dean McDermott Welcome Baby No. 5!
As for her husband, he's seen sipping red wine in the photo and sporting a shirt that reads: "Drinking for two."
A post shared by meganhilty (@meganhilty) on Sep 24, 2016 at 5:01am PDT
Hilty isn't the only celebrity to have a March baby! ET confirms that Backstreet Boys singer AJ McLean also welcomed his second daughter, Lyric Dean McLean, with wife Rochelle on Sunday.
WATCH: Geri Halliwell Welcomes Baby No. 2 on Baby Spice's Birthday
Here's a look at what McLean told ET about raising girls:Read more at Entertainment Tonight