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The genus Mammillaria is the most diversified in the Cactaceae. Mexico is center of this diversification, however studies that analyze the life cycles of these species are needed to help in population diagnostics and provide management information for their conservation. Mammillaria humboldtii is an endemic species of Hidalgo, currently listed as "threatened" by Mexican legislation (NOM-059-SEMARNAT-2010) and the IUCN lists it as "critically endangered". The study employed matrix projection models to evaluate a population of M. humboldtii within the Metztitlan Canyon Biosphere Reserve. A one year transition matrix was constructed from which the finite population growth rate (X) was determined. Changes in matrix elements corresponding to the permanence in the seed bank, transition from seed to seedling and adult stasis were simulated. The population growth rate was below unity (k = 0.7931, CI = 0.7797-0.8050) indicating a decreasing population over time. Stasis (S = 70.05 %) was the process that contributed the most towards k, followed by growth (G = 15.69 %). The highest reproductive value was for those adults in size class 3, and the simulations showed that increasing seedling establishment and survival of adults increased the value of lambda > 1, suggesting these processes as the main bottlenecks in the dynamics and population growth. Any management strategy for the in situ conservation of this species should consider long term monitoring of the population to ensure seedling establishment and survival or adults.