Smith, who the Cowboys view as a cornerstone of their future, is guaranteed $40 million and will receive a $10 million signing bonus, according to sources. He had two years remaining on his previous contract after the Cowboys picked up the fifth-year option of his rookie deal in the spring.
"Late last week, the Cowboys approached me with a deal I told my agents I wanted to sign," Smith said in a statement released by his marketing firm. "My agents explained the pros and cons of this deal versus one that may be shorter term and/or higher guarantee. After careful consideration, I decided this long term deal was exactly what I wanted.
"Over the past three years, the Cowboys organization and Jones Family have helped me through trying times and I felt this was my opportunity to return the gratitude. I am beyond grateful for the Cowboys staff, my teammates, and the fans, and wanted to ensure I was locked in as a 'Cowboy for Life.' I want to thank everyone for their support and look forward to having a star on my helmet for the remainder of my career."
Cowboys coach Jason Garrett said it was important for the team to lock up a young, key piece.
"We talk about building a program and building a football team and he was the first player that we took three years ago in that draft," Garrett said. "He's just been everything we've wanted to build this program and this team around. He was really a young player, who we put in really on minute one of day one and he's everything that we thought he would be, both physically, intangibly and just as a person. His work ethic is fantastic. His mental and physical toughness are as good as I've been around. He just continues to grow and develop as a player. Technically he's getting better. He's getting bigger and stronger. And he's just tough, competitive. He's what you want on your football team at a really, really important position."
Smith is the second member of the 2011 draft class to sign a lucrative extension in as many days, joining Arizona Cardinals cornerback Patrick Peterson, who signed a five-year extension worth $70 million.
Smith became the first offensive lineman drafted by the Cowboys in the first round since 1981 when he was selected with the ninth overall pick of the draft. He has started all but one game since joining the Cowboys and moved to left tackle in 2012.
"Something that wasn't an argument is that we felt that based on his skill, based on his age, that Tyron deserved to be the highest paid left tackle," executive vice president Stephen Jones said. "It's just how we were going to go about doing it."
The Cowboys have been in negotiations with his agents through the spring and talks picked up recently.
Smith does not turn 24 until December and will be able to hit free agency again by the time he is 32. Smith is considered a prototype left tackle with his athleticism and strength and was selected as a second-team All-Pro in 2013.