The present study analyzes the diversity and abundance of infraorder Brachyura megalopae and their relationship with the environmental factors in the Jamapa River estuary, Veracruz, México. The environmental factors of dissolved oxygen, water temperature, total dissolved solids, pH, and salinity were measured. Crabs were captured using light traps and shrimp bait. The generalized linear model was used to determine the relationship between the environmental factors and the five sampling months and the five sampling sites and was used to determine the relationship between the abundance of the megalopae and the sampling months, sites, and environmental factors. A total of 5398 megalopae belonging to seven species of Brachyura were collected. The most abundant species were Minuca vocator and M. burgersi, with 2174 and 2156 megalopae, respectively; these species are common in low-salinity estuaries. The highest diversity was found at the southern boundary of the estuary with six species, 2.24 bits ind-1. The statistical analyses showed that the values of the environmental factors related to the climatic season determine (i.e. temperature and salinity) the abundance of the megalopae. Based on the diversity values evaluated, it can be established that the Jamapa River estuary has intermediate stability.