Jackson finished his college career with 177 receptions for 3,548 yards (20.0 average per catch) and 37 touchdowns. He also returned 88 punts for an 11.6-yard average and two scores. In 2004, he caught a school-record 80 passes for 1,382 yards and 11 touchdowns.
"He's a terrific athlete and we're glad to get him here," General Manager A.J. Smith said. "We wanted to give Vincent a deal that was fair for him and fair for us. We're pleased that we were able to do that."
Shawne Merriman remains the only unsigned pick heading into full squad workouts on Friday.
The Chargers also announced Thursday that linebacker Carlos Polk has been placed on injured reserve with a torn Achilles tendon.