We love their love!
"You're not only my wife and the mother of my children, you're my best friend," he wrote. "I love your strength, your grace and your determination. And I love you more each day."
In the photo he shared, he's looking lovingly at his wife of 25 years, with a smile on his face.
The former first lady celebrated her 54th birthday on Wednesday.
She also posted on Instagram to share a photo of the card and flowers he gave her.
"Thank you @BarackObama for the beautiful flowers waiting for me in the office this morning," she wrote. "You're my best friend, biggest fan, and getting notes and flowers from you will never get old."
She thanked people who sent cards from around the country and wrote birthday messages to her on social media.
"You have no idea how much we love hearing from you," she wrote. "I know birthdays can sometimes be bittersweet (54!), but your messages of hope, generosity and warmth have always reminded me how lucky and blessed we are."