Moore also shared an adorable birthday video message during a recent stop on the TODAY show, where she expressed excitement at returning to the set this month to start shooting season 2.
"Mi! Happy birthday! Oh my goodness, I'm excited to see you soon and get back to work," she said. "You are the best -- you know how much I love and adore you and I hope that this year brings everything you want. You deserve it all. And, I can't wait to celebrate with you in person. Happy, happy birthday."
The star has had nothing but kind words for her "TV husband" and told ET back in January that he's "such a special guy."
"It's really not hard to have to just love him," Moore gushed of her affection for Ventimiglia. "I feel incredibly lucky every day just to have this job, but then to get to work with him every day, too."
The actor responded on Twitter to the outpouring of love on his special day.
"Been waitin 40 years to wear this hat," Ventimiglia said, alongside a snapshot of himself wearing a hat with the iconic "Over the Hill" birthday catchphrase. "It fits real nice. Thanks for all the birthday wishes y'all. Lots of love."
This Is Us returns for season 2 on Sept. 26. For more on Moore's friendship with Ventimiglia, watch the clip below.