The 32-year-old star and husband John Legend are already parents to one-year-old daughter Luna.
After attending the 60th Grammy Awards, Teigen announced the gender of her second child while sharing a picture of herself from the red carpet.
"Mama and her baby boy," she captioned the photo on Instagram.
For the event, Teigen opted for a silver Yanina Couture gown featuring long bell sleeves, cinched at the waist.