Charlton fans can get an extra 25% off all stock in the Valley Superstore on Saturday between 9am and 2pm.
Items available include replica kits, training and leisure wear, gifts and souvenirs with the additional discount applied at the till.
Charlton face already-promoted Blackburn Rovers on Saturday and will be hoping for a win to keep their play-off hopes on track.
Manager Lee Bowyer has called for a large crowd to replicate the fantastic support by the fans away to Portsmouth last week.
Information on purchasing tickets to the Blackburn game can be found here.
Supporters are advised to arrive in good time, with a larger crowd than normal expected for the big game, which could result in long queues.