Manning sat out Wednesday's workout due to a sprained right ankle, an old injury that the quarterback aggravated in last Sunday's game.
The Broncos play host to the Kansas City Chiefs Sunday night. The Chiefs (9-0) have the best record in the NFL while Denver is 8-1 and a game behind in the AFC West. The teams are to play each other again Dec. 1 in Kansas City, Mo.
Manning's status has been a concern since he came up limping after throwing a pass that helped the Broncos defeat the San Diego Chargers 28-20 last week.
Asked if Manning would be available Sunday, Del Rio said: "No doubt. He participated a little bit at walk-through today but he'll be ready to roll on Sunday."
Manning said Wednesday, "I was able to go to the walk-through but spent the rest of the time getting some treatment and was a part of all the meetings to get a head start on the mental aspect of things heading into this weekend."
Manning has completed 71 percent of his passes for 3,249 yards and 3 touchdowns this season.
Del Rio is filling in for Broncos Coach John Fox, who is in North Carolina recovering from surgery to replace a heart valve.
Fox said Tuesday in a conference call with Denver-area media that he would return to Denver as soon as he was cleared to fly. He said he set a goal of being on the Bronco's sideline by the end of the season.