The Pro Bowl left tackle signed an eight-year, $98 million extension Wednesday that pushes the total value of his deal to $110 million over 10 years, locking him up through 2023.
The extension includes a $10 million signing bonus and $40 million in guaranteed money. Smith joins Romo as the only Cowboys with contracts valued at more than $100 million.
Smith was just 20 when the Cowboys took him ninth overall in 2011 out of Southern California. That was Jason Garrett's first draft as coach.
''That first one says a lot about what you believe,'' Garrett said. ''He's something else. We really emphasize the importance of mental toughness. We believe that's a distinguishing trait in players and in teams. And he represents that in spades. He's off the charts.''
In a statement through his marketing agency, Smith said the Cowboys approached him with what is a cap-friendly deal for the franchise, and the lineman asked his agents to weigh the pros and cons of signing it.
Smith said part of his reasoning was rewarding owner Jerry Jones for standing by him during a difficult time that included Smith's lawyer accusing the player's parents of taking money from him after he had set up a way to give them a portion of his rookie contract.
''They've looked out for me and I just wanted to look out for them,'' Smith told reporters after Wednesday's late practice. ''The deal they offered me, didn't really need much and it's something I was really comfortable before I took it.''
Executive vice president Stephen Jones said the Cowboys wanted to make Smith the highest-paid left tackle in the NFL, which he said was accomplished through a $12.2 million average for the eight-year extension.
''Tyron deserves it,'' Jones said. ''He's 23 years old, and it may be the first 10-year deal I've ever done in football where I think the guy will be playing in the last year of his contract.''
Smith has started all 47 games in his career, missing one game with a sprained ankle in 2012. He played right tackle as a rookie before moving to the left side, and this year he'll be protecting Romo's blind side with the 34-year-old coming off back surgery.
''He's just been everything we wanted to build this program and this team around,'' Garrett said. ''He was a really young player we put in really in minute one of day one. He's everything we thought he was going to be, physically and intangibly and just as a person. His work ethic is fantastic.''
Smith became the first-round model in three of four drafts for the Cowboys - proven players from major college programs.
They took center Travis Frederick from Wisconsin late in the first round last year after trading down and grabbed right guard Zack Martin out of Notre Dame in the middle of the first round this year.
''On draft day, you're optimistic about the players you take, particularly that high in the draft, but when you see them develop as quickly as he has into the kind of leader and the player you want, not only for your team but your program, it's really satisfying,'' Garrett said. ''He's a cornerstone player in this franchise.''
As with Smith, Frederick and Martin have been plugged in as starters from the start of their first offseason. They were born within four months of each other and will each be 23 when the season starts.
''You see those relationships developing before your eyes,'' Garrett said. ''It's a special bond, particularly when you play a position like offensive line where the communication is verbal but also has to be almost by feel.''
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