Objective: the purpose of this in vitro study was to measure the temperature increase induced during visible light curing of four different shades of resin composite by measuring the infrared emission from the surface of the curing resin composite. Methods: in this study, four shades of a hybrid resin composite (Spectrum, Dentsply, Weydridge, UK) were selected; two shades at the extremes of the shade guide (B1 and A4) and two commonly used shades in the middle of the shade guide (C2 and B3). The composite was packed into polytetrafluoroethylene (PTFE) moulds and cured for 40s using a quartz-tungsten-halogen (QTH) curing unit (Dentsply, Konstanz, Germany), with an intensity of 530mW/cm2. Temperature rise on the undersurface of the curing composite was measured using an infrared thermal imaging camera (Thermovision 900, Agema, Danderyd, Sweden). Forty specimens of each shade were tested and the mean values calculated from the forty measurements. Results: the maximum temperature increases of the composite samples tested were: (56.69°C±1.15) for shade C2, (56.07°C±1.08) for A4, (55.29°C±1.34) for B3 and (55.61°C±1.36) for B1. ANOVA indicated statistically significant differences (p<0.001) between all shades. Conclusions: there was a quantifiable amount of heat generated in resin composite during light curing. Lighter composite shades produced higher initial temperature rise than darker ones. However, the darker shades produced higher overall temperature rises during the course of curing.