The couple broke the news in the debut edition of the magazine version of Paltrow's Goop website.
"We feel incredibly lucky to have come together at this junction in our lives when our collective successes and failures can serve as building blocks for a healthy and happy relationship," the two said in a joint statement, as reported by E! Online.
The 'Iron Man' star and Martin only finalised their divorce in July 2016.
Talking about the divorce, she said, "[It] used to feel like a failure; it took me a while to reframe that divorce isn't a failure."
The actress had been dating Falchuk for three years, and reports of their engagement have been swirling since November.