Mason announced the injury Thursday.
Jelks hurt his knee during a team drill at practice Wednesday when the Commodores worked indoors. The redshirt junior started 12 games last season at left tackle and 22 games over the past two seasons on the offensive line.
Mason says he's really disappointed for Jelks who was having a great camp.
The Commodores also lost wide receiver C.J. Duncan to a season-ending injury last week.
Vanderbilt opens the season Sept. 3 hosting Western Kentucky.