"Happy Birthday, my Bean. 15 years old today!!" the actor wrote."When you were born it took about 2 seconds to realize that I was willing to die for you. Thank you for correcting my heart -- and teaching me how to love without constriction or condition."
Included with the message was a throwback photo of the proud dad carrying a young Willow.
In October, Will returned to music with his first single in 10 years by teaming up with Colombian band Bomba Estéreo for a remix of their song "Fiesta." The popular tune was nominated for record of the year at the 16th annual Latin Grammy Awards where the 47-year-old is set to perform.