The stabilities of different BODIPY dyes in chloroform under gamma radiation exposure (up to 300 Gy) were checked for their use in gamma dosimetry. Bare BODIPYs were highly stable as compared to the methyl and ethyl substituted BODIPYs. Using bare BODIPY dye, 8-(N,N-dimethylanilino) BODIPY, a ratiometric fluorescence “off-on” dosimeter with 0.5 Gy limit of detection and 0.5–150 Gy detection range is developed. This is the first report of a ratiometric fluorescence gamma dosimeter using BODIPY dye.