Seed germination in Melocactus and other cactus species is hampered by the occurrence of dormancy. However, most studies failed to achieve high seed germination rates, suggesting a complex mechanism of dormancy in Cactaceae. Thus, the objective of this study was to demonstrate that dormancy in Melocactus seeds may be associated with factors such as light and phytoregulators. Two consecutive experimental sets were designed: one with seed germination paper under different wavelengths and Photosynthetically Photon Flux Densities (PPFDs); and one in vitro experiment using a culture medium to evaluate the influence of different plant growth regulators, both in the germination of seeds of Melocactus zehntneri. The results obtained showed that seeds of M. zehntneri are positive photoblastic. Red light and gradual increases in PPFD resulted in the highest germination rates and speed germination index. The experiment with phytoregulators showed a major effect of Ethephon to release the germination of dormant seeds of M. zenhtneri, totalizing 98% of seeds germinated under in vitro conditions, compared to 76% in control. The present study develops an efficient technique to break seed dormancy and the results can be useful to better understand cacti seed dormancy.