Watt and Ohai announced the engagement Sunday on social media. They have been dating for three years.
"I'm the luckiest man in the world," Watt wrote on Instagram. "#SheSaidYes."
Watt popped the question while the couple vacationed. He bent his knee at the end of a pier while flanked by flowers and candles.
"Still can't believe I get to be with you forever. I love you J.J. Watt," Ohai wrote on Instagram.
Ohai, 27, plays for the Houston Dash of the NWSL. Her sister is married to Watt's former teammate, Brian Cushing.
"We texting and you don't even bring this up? Wow! Congrats, brother," Timberlake wrote.