He revealed the news of his invitation on Monday in an interview on WJR Radio.
"I did invite him out to training camp," Wood said Monday on WJR. "We'll see if he does that. Hopefully he shows up and he's a great player. We want to have him in the tent and not outside the tent."
Wood said he exchanged text messages recently with the three-time All-Pro. Johnson, 31, announced his retirement in March of 2016. He played his entire nine-year career with the Lions.
Johnson said that the team's history of losing had to do with his departure. He told the Italian press recently that his ultimate goal was to win a Super Bowl and "didn't see that opportunity" with the Lions.
"I didn't see a chance for them to win a Super Bowl at the time," Johnson said. "For the work I was putting in, it wasn't worth my time, to keep on beating my head up against the wall and not go anywhere."
But if Johnson did decide to comeback, it would likely have to be for the Lions.
"I was stuck in my contract with Detroit, and they told me they would not release my contract, so I would have to come back to them," Johnson said. "I didn't see the chance for them to win a Super Bowl at the time, and for the work I was putting in, it wasn't worth my time to keep on beating my head against the wall and not going anywhere."
The training camp invite is a bit mysterious, after rumored tension regarding Johnson's relationship with the franchise.
"I don't even like to talk Lions too much just because the way our relationship ended," Johnson told the Detroit Free Press . "If they see me around here, we'll see. But hey, I don't know."
"I just didn't feel like I was treated the way I should have been treated on the way out. That's all. I mean, it's all good. I'm not tripping. I don't feel any kind of way, just hey, that's what they did. Hey, it is what it is."
A source told the Detroit Free Press that when he retired, Johnson paid the Lions back at least $1 million from his contract. He signed an eight-year, $132 million contract with the Lions in 2012.
Johnson is the Lions' all-time leader in receiving yards, catches and receiving touchdowns. In 2012, "Megatron" set the NFL record for receiving yards in a season with 1,964.
Lions camp begins on July 31 and runs through August 7. The Lions' first preseason game is August 13 against the Indianapolis Colts at Lucas Oil Stadium in Indianapolis.