Aim: The objective of this study was to evaluate the effect of additional light curing on the colour stability of composite resins. Materials and methods: Four different composite resins-a nanofill, a nanohybrid, a microhybrid, and a bulk-fill composite resin-were tested. Eighty disc-shaped specimens were prepared from each material using either a quartz tungsten halogen or a light-emitting diode light source and were randomly divided into 2 groups according to the surface treatment: no polishing (nonpolished) or polishing with aluminum oxide discs (polished). Then additional light curing was applied to half of the specimens in each group. All specimens were immersed in coffee solution for 1 week. Colour was measured with a spectrophotometer at baseline and after 1 week of storage in coffee solution. Results: Statistically significant differences in colour stability were observed in the restorative materials according to the composition of composite resin, the polishing protocol, and additional light curing, whilst there were no significant differences according to the light source. Additional light curing reduced discolouration in all groups tested. Conclusions: Additional light curing may be beneficial after finishing and polishing in order to maintain aesthetics and increase the resistance of composite resins to discolouration. (C) 2021 The Authors. Published by Elsevier Inc. on behalf of FDI World Dental Federation.