The effects of washing treatment on hatching rate of eggs and survival rate of nauplii and postlarvae (PL) of Penaeus monodon was studied at a commercial hatchery of Bangladesh during the period of November 2008 to October 2009. The experiment was set up with two groups for each of P. monodon eggs, nauplii and PL, viz., i) washing treatment (treated group), and ii) without washing treatment (control group) in triplicate. The hatching, nauplii and PL survival rates were significantly higher (p<0.05) in treated group over those of control group. The mean hatching, nauplii and PL survival rates were 76.6±13.2, 76.4±8.7 and 79.6±9.1% in treated group and 30.0±6.9, 48.8±7.0 and 53.8±8.7% in control group, respectively. Hatching and survival rates of nauplii and PL were noted with better performance in winter, spring and autumn than that in summer. The observations from this study could be useful for larval rearing of P. monodon in areas where shrimp hatchery system is a promising industry.