Abstract Mg 2SiO 4: Tb TLD phosphor was found to show enhanced TL sensitivity to both gamma and UV radiations after high pre-gamma exposures (>100 R) and a post-annealing treatment at 300°C for 1 h. Maximum sensitization factors of 2.8 and 55 were obtained at the pre-exposure levels of 5.2×10 1 C/kg and 1.3×10 3 C/kg for gamma and UV test radiations respectively. The near constancy of the intensity of the residual TL (RTL) peak at 500°C for the sensitized sample with increasing test-gamma exposures has ruled out the re-trapping model proposed earlier for the gamma radiation induced sensitization in this phosphor. The T max for the sensitized phosphor was found to occur at a higher temperature compared to that for the virgin phosphor. The dependence of sensitization on RTL was explained qualitatively on the basis of competition between sensitization traps (having higher energy than the dosimetry traps) and RTL traps while capturing the charge carriers generated during the test-gamma exposure. The sensitization observed in this phosphor to UV test radiation was found to be a consequence of the photo-transfer of charge carriers from deep (RTL) traps to the shallow (dosimetry) traps. The reduction in RTL peak (500°C) intensity of the sensitized sample with increasing test-UV exposure has demonstrated the photo-transfer mechanism in this phosphor. The TL response of the virgin Mg 2SiO 4: Tb phosphor was found to be supralinear to both gamma and UV radiations. The TL response of the sensitized phosphor was found to be linear to gamma radiation and sublinear to UV radiation.