We examined the tolerance of greasyback shrimp Metapenaeus ensis to hypoxia and H₂S exposure under controlled laboratory conditions. Larvae and juveniles were exposed to normoxic or to hypoxic water (dissolved oxygen concentration <0.5 mg/L) with or without un-ionized H₂S (concentrations, 0.09 to 0.62 mg/L). One-hour exposure experiments revealed ontogenetic changes in the shrimp’s tolerance to hypoxia and H₂S exposure: tolerance to hypoxia was high in larvae at nauplius (survival rate, 100%) and protozoea stages (79%), but was attenuated significantly in larvae at mysis and postlarval stages as well as in juvenile stage (0% for these stages). Presence of H₂S of the concentration >0.1 mg/L enhanced decrease in the survivability after the one-hour exposure even in the hypoxic-tolerant nauplius and protozoea stages. Larvae and juveniles ceased swimming behavior and sank to the bottom soon after the initiation of exposure to hypoxic water with H₂S, followed by death within 24 hours. These results suggest that mass mortality of larvae and juveniles of greasyback shrimp could occur by exposure to hypoxia and H₂S in the field.