The Mexican-American actress wrote a sweet Instagram post for Augustin James Evangelista to commemorate his 18th birthday on Friday, October 11.
"Happy 18th bday Augie you're officially a full grown up man who just became legal at least in Mexico and France," she captioned a series of family and personal photos.
"Your gentle heart is like healing caress in our lives because you bring warmth and light to everyone around you. Keep bringing the laughter and joy. We love you so much," continued Hayek in her post.
Augustin is Hayek's stepson through her marriage to his father, French businessman Francois-Henri Pinault.
Hayek married Pinault, 62, at a courthouse in Paris on Valentine's Day, 2009, before hosting a second, grander ceremony in April. The twosome share a daughter, Valentina, now 16.
Augustin's mother is supermodel Linda Evangelista, who also commented on the birthday post for her son. "1️⃣8️⃣ years of 💞," she noted.
Hayek recently celebrated her own birthday, marking her 58th year on September 2 by posting a series of bikini thirst traps via Instagram.
"Birthday bikini dump, happy 58th birthday to me! 🎂❤️🎉P.s none of these are throwbacks," Hayek captioned the photo carousel, in which she sports a variety of bold and colorful swimsuits while vacationing atop a boat on the Mediterranean.
The comment section soon flooded with birthday messages for Hayek.
"58 couldn't look better. Happy birthday mama ❤️," wrote Vanessa Hudgens, while Sharon Stone said, "Happy birthday you."
Hayek recently made headlines for opening up about her time on the set of the movie Without Blood, working with Angelina Jolie and her kids. She noted that Jolie was "very professional" with sons Maddox, 23, and Pax, 20, on set.
"She's demanding. They got the respect of the crew, and they were good with the crew, and they were very in their place," Hayek said. "They were not treating me like they treat me outside of there. They were very, 'You have to come,' and I go, 'OK!' It was kind of fun."
"They work hard. They are very serious about what they do," Hayek continued.
In the new drama, Hayek plays Nina, who is dealing with the aftermath of an unspecified war. Hayek told Entertainment Weekly that Jolie, 49, had to convince her to take the part.
The Frida actress and socialite enjoyed a festive summer, from sitting courtside at Wimbledon, to watching Taylor Swift perform at London's Wembley Stadium, to carrying the Olympic torch amid the Paris games.
Earlier this year, she offered her social media followers a rare glimpse of her wedding to Pinault, who is the president of luxury fashion conglomerate Kering, which owns Gucci, Yves Saint Laurent and Alexander McQueen, among other high-fashion brands.
