Abstract: The present study reports the sex ratio and fecundity of four prawn species (Macrobrachium lamarrei, Macrobrachium malcolmsonii, Macrobrachium dolichodactylus and Macrobrachium dayanus) from the northeast (Sylhet, Maulavi Bazar and Sunamganj districts) and northwest (Pabna, Sirajganj and Natore districts) parts of Bangladesh. Females were more common than males in each species with male-female being 1:17.5, 1:1.1, 1:2.6 and 1:1.6, respectively, although this result was statistically significant only for the first species. Fecundity (mean ± SD) of the studied species was found to be 228 ± 69, 6234 ± 2390, 2187 ± 729 and 153 ± 22 eggs per female, respectively. Fecundity in all the species was found directly related to total length, standard length and total weight.