Fox was taken to a hospital in Charlotte, North Carolina, after feeling light-headed while playing golf on November 2 and had an aortic heart valve replacement two days later.
"I feel as healthy as I've ever felt over the last 20 years," Fox, 58, said. "Our team is still in good position.
"I had open-heart surgery and watching those games was harder than any pain I felt."
In Fox's absence, defensive coordinator Jack Del Rio went 3-1 as interim head coach, including Sunday's 35-28 win over the AFC West rival Kansas City Chiefs.
With the win the Broncos took control of the division with a 10-2 record while the Chiefs slipped to 9-3.
Fox, who was the coach of the Carolina Panthers for nine years and is now in his third year with the Broncos, could spend his first game back on Sunday against the Tennessee Titans coaching from the booth, according to report on NFL.com.
"I'm getting back into the flow," said Fox. "We'll see how I react to everything as I move forward."