Sources told ESPN's Adam Schefter the deal is worth $43 million.
Boyd, who was entering the final year of his rookie deal, will now be under contract through the 2023 season.
Selected in the second round of the 2016 draft, Boyd has become one of the Bengals' most important players on offense, dating back to the end of the 2017 season.
"We think very highly of Tyler and are thrilled to get him in the fold for the next few years," Bengals coach Zac Taylor said in a statement. "After I joined the team in February, while reviewing video of all the team's games last year, he was one of the first players that stood out to me as being a hard worker and improving steadily throughout the season. I have also gotten to know him as a person since I arrived, and it was obvious to me early on that it would be a good thing for us to seal him up for the foreseeable future."
"It's a good thing for the team. He's a fine player. He's proven it," Bengals owner Mike Brown said of Boyd prior to the announcement of the extension. "We try to extend the guys that matter and we see him as a player who is a difference-maker. He's a solid guy, he competes, he makes big plays, he doesn't scare. He has the ingredients that we look for in a wideout."
Cincinnati's top wideout, A.J. Green, is heading into a contract season. Bengals player personnel director Duke Tobin said it's not an either/or situation -- the team would like both receivers to get new extensions -- and Green's age (31 on July 31) and injury history (hamstring issue in 2016, toe injury in 2018) aren't deterrents to the team.
"Both good players, we'd like to retain both of them, and we'll see what we can get done as we go here," Tobin said. "Obviously Tyler has earned it, he's come on, he's a big part of our offense. As a young player, he's got a lot of upside, so we're excited to have him back for the long term.
"I expect no drop-off from AJ."
Added Brown: "A.J. is a great player, and one thing I've learned is that great players have a tendency to keep on longer. They just have more in the tank. And I think that applies to A.J. Yes, he is going to be in his 30s and we can all count. We know that eventually things end, but I don't think it's now for him."