We investigated the toxicity of acidic and alkaline pH and its effects on hepatopancreas of prawn Litopenaeus vannamei at long term and short term exposure. After exposure of different pH conditions such as 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5, 10.5 for 24 hrs, 7th days, 15th days, 21th days and 30th days, the results showed that there was change in the histoarchitecture of hepatopancreas during acute exposure of acidic pH (24 hrs). Vast structural damages were found along with degenerative changes. At extreme acidic pH (3.5) high structural damage of hepatopancreas was observed. At extreme basic pH (10.5) mild structural damage of hepatopancreas tissue was identified. However during chronic exposure majority of prawns below 6.5 pH were died. They were not able to survive at extreme lower pH. There is no much structural differences at 6.5 pH. The prawn Litopenaeus vannamei was better tolerated at extreme basic pH up to 9.5. Only mild degenerative changes were found at 10.5 pH. The detailed histopathological changes that were recorded at altered pH media were discussed in the present study.