The freshwater prawn Macrobrachium jelskii (Miers, 1877) is widely distributed in South America's lentic and lotic habitats. We studied the population structure and reproductive biology of the species in the municipality of Cruz das Almas, state of Bahia, Brazil, to supply information on this ecologically and economically relevant species. Samples were collected monthly, from February 2013 to January 2014, at Laranjeiras pond. The sex ratio was biased towards females (1.4 females : 1 male). The mean carapace length of females and males was respectively 8.08 ± 1.37 mm and 6.61 ± 1.11 mm. Ovigerous females comprised 22.5% of all sampled females, and their reproductive activity, characterized as seasonal-continuous, was positively correlated with precipitation. The average size of females at the onset of functional maturity was estimated at 6.67 mm CL and the mean fecundity was 25.2 ± 8.9 eggs. Egg size, mass and volume increased significantly during embryonic development. Our data strongly indicate that the reproductive strategy that best fits the species is the "pure search" mating system.