Graham's contract is worth $11.25 million, a source told ESPN NFL Insider Adam Caplan.
Graham, 27, became the Texans' starter last season when Owen Daniels went on injured reserve with a nondisplaced fibula fracture after Week 5. The fourth-round draft pick out of Wisconsin in 2010 finished the year with 49 receptions for 545 yards and five touchdowns.
Prior to Graham's agreement, the Texans were the only team to have not signed or re-signed a player since the new league year began Tuesday.
Houston released Daniels, who turns 32 in November, on Tuesday. The move gained the Texans $4.5 million in salary-cap space, but they made it without an assurance Graham would return.