Gibson, who had anchored "Good Morning America," replaced him on "World News Tonight" when Woodruff was injured in a January bomb explosion.
Woodruff was unconscious for 36 days following the attack. He suffered head injuries and shrapnel wounds, the network said.
Thursday was Woodruff's second visit to the newsroom, TV Guide reported.
"I woke up in this hospital and I looked up and I just thought about you guys and I thought about everything I wanted badly to come back to," Woodruff told colleagues two weeks ago, the New York Post said.
There were some initial reports his injuries slurred his speech and movement, but Woodruff seemed unaffected during his studio visit in early June, the newspaper said.