"Tony is uniquely qualified to lead this team at the quarterback position for the next several years," Jones said. "He knows how to run an offense and run a team."
Romo lost playoff-or-bust games in regular-season finales the past two years. That included a loss to Washington last season when Romo threw an interception with a chance to tie or win the game with a drive in the final 3 minutes.
A former Romo rival, Donovan McNabb, questioned the deal on Twitter.
"Wow really, with one playoff win," McNabb wrote. "You got to be kidding me."
Dez Bryant, who teamed with Romo for career highs of 1,382 receiving yards and 12 touchdowns in 2012, tweeted, "Congrats Big Tony on the contract extension."
Romo is the franchise leader in touchdown passes and the single-season leader in touchdowns, passing yards, completions and attempts. He had a career-high 4,903 passing yards in 2012 but matched his highest interception total at 19 and had his lowest quarterback rating at 90.5 rating.
His best rating of 102.5 came in 2011, when the Cowboys lost to the New York Giants with a playoff berth on the line in the finale. His other best season was 2009, which included his only playoff win against Philadelphia.