Background: Molar-incisor hypomineralisation (MIH) is a qualitative enamel defect. Aim: To investigate the low-level laser therapy (LLLT) associated with fluoride varnish for the desensitisation of teeth with MIH. Design: A randomised clinical trial was conducted with 66 children, randomly allocated to the treatments: laser (L); fluoride varnish (FV); and laser + fluoride varnish (L + FV). The participants in the L group underwent two sessions of LLLT (48-hour interval). The FV group received four applications of varnish at one-week intervals. The L + FV underwent two sessions of LLLT and four applications of varnish. Prior to each session and one month after the onset of treatment, tooth sensitivity and its magnitude were evaluated. Intra-and inter-group comparisons were performed (α = 5%). Results: A significant reduction in the mean sensitivity score was found over time in all groups. After the final treatment, a significant difference was found between the L and L + FV groups (P = .011), with a lower score in the L + FV group (0.09), whereas no difference was found between the FV and L + FV groups (P = .095). Conclusions: Fluoride varnish and the combination of treatments (L + FV) had greater desensitising action on teeth with MIH. Laser therapy demonstrated an immediate desensitising effect, whereas fluoride varnish had a late-onset effect. K E Y W O R D S child, dentine sensitivity, fluoride, topical, low-level laser light therapy, tooth demineralisation 324 | MUNIZ et al.