The guinea grass Panicum maximum, an African grass, is one of the main forage grasses in tropical America. Its propagation is mainly carried out by seeds, but seed dormancy hampers good pasture establishment. The aim of this study was to evaluate the use of heat treatment to overcome seed dormancy of P. maximum cultivars Milênio, Tanzânia and Mombaça. Seeds of each cultivar have been subjected to heat treatments at temperatures of 50, 60 and 70°C with exposure time for 5, 10 and 15 h. Afterwards, they were placed in germination test. The data were subjected to analysis of variance and, when significant, polynomial regression was performed, with up to 5% of probability. The variables analyzed were germination percentage, germination speed index (GSI) and average germination time (AGT). P. maximum seeds of different cultivars showed distinct responses to heat treatment. The cultivar Tanzânia responds positively to different combinations of temperature and periods of seeds exposure, and the treatment at 70°C for about 8 h is recommended to overcome dormancy with better germination performance. For cultivar Milênio, it is recommended the exposure of seeds at 70°C for 15 h. Cultivar Mombaça is negatively influenced by the heat treatment, so this treatment is not recommended.