The agreement was reported on the team's website Friday. The deal will lower Romo's salary cap number of $16.8 million for 2013, giving the team more room to sign free agents and draft picks.
Romo, who turns 33 next month and was entering the final year of his contract, gets $55 million guaranteed and could be with Dallas through 2019. Super Bowl winner Joe Flacco got $52 million guaranteed in the six-year, $120.6 million contract he signed with Baltimore earlier this month.
Romo is the franchise leader in touchdown passes but has just one playoff win in six full seasons as the starter.
