A novel method of calibrated doping of Mn in ZnS thin films has been used to study room‐temperature cathodo‐ and photoluminescence characteristics of ZnS:Mn films for a Mn concentration range of 0.07–26.4 wt. %. It was observed that the luminescent intensity increases with Mn concentration up to ∼2 wt. %, beyond which intensity decreases. Emission spectra revealed a lower energy peak in addition to the 580‐nm yellow peak for higher dopant concentration. The occurrence of this red peak and quenching of yellow emission is probably at approximately the same activator concentration (∼2 wt. %). We attribute these to the phenomenon of energy transfer to energy sinks via unexcited Mn.