Luminescence of CdS quantum dots (QDs) enhanced by the induction of Ag nanoparticles (NPs) in glasses was investigated. Ag+ ions diffused into glasses containing CdS QDs by ion exchange, then formed Ag NPs after subsequent heat treatment. Luminescence intensity of CdS QDs increased approximately three times when the ion-exchange duration was 1 min, but was severely quenched when the duration was extended to 30 min. Increasing the amount of Ag+ ions increased the number of Ag NPs and decreased the average distance between Ag NPs and CdS QDs. This decrease in the average distance induced the changes of luminescence intensity.