Objective: To investigate the effects of spectral overlays on reading performance of Brazilian elementary school children. Methods: Sixty-eight children (aged 9–12 years) enrolled in the 5th and 6th grade were included in the study. The Rate of Reading Test (RRT – Brazilian Portuguese version) was used to evaluate reading speed and the Irlen Reading Perceptual Scale was used to allocate the sample according to reading difficulty/discomfort symptoms and to define the optimal spectral overlays. Results: A total of 13% of the children presented an improvement of at least 15% in reading speed with the use of spectral overlays. Pupils with severe reading difficulties tended to have more improvement in RRT with spectral overlays. Children with severe reading discomfort obtained the highest gains in RRT, with an average of 9.6% improvement with intervention, compared to a decrease of –8.2% in the control group. Participants with severe discomfort had an odds ratio of 3.36 to improve reading speed with intervention compared to the control group. Conclusion: The use of spectral overlays can improve reading performance, particularly in those children with severe visual discomfort.