The indiscriminate use of herbicides has led to the contamination of water bodies, possibly affecting the health of aquatic biota, especially fish. Atrazine is considered as toxicants for aquatic fauna, due to its high persistence in soil, high half-life and high mobility toward aquatic bodies as well as high solubility in water. The objective of the present study was to determine (LC₅₀) and to evaluate the acute and chronic toxicity of atrazine on the biochemical parameters; total protein and serum albumin of freshwater grass carp (Ctenopharyngodon idella). Above 15 μlL^-1, the LC₅₀ was recorded revealing sensitivity of grass carp to atrazine. Grass carp was exposed to atrazine for 01 (15 μlL^-1), 02 (13 μlL^-1), 03 (10 μlL^-1), and 04 (08 μlL^-1) days/concentration for scrutinizing acute toxicity. Likewise, fish were exposed to atrazine for 10 (06 μlL^-1), 15 (04 μlL^-1), and 25 (02 μlL^-1) days/concentration for scrutinizing chronic toxicity. Control group concentration was 8.3 gL^-1 and 3.5 gL^-1. Total protein concentration observed for acute toxicity was 7.5 gL^-1, 6.5 gL^-12, 4.6 gL^-1, and 3.2 g/L and serum albumin concentration was 2.7 gL^-1, 1.6 gL^-1, 1.4 gL^-1, and 1.1 gL^-1 respectively. Similarly total protein concentration observed for chronic toxicity was 8.2 gL^-1, 6.8 gL^-1, and 4.3 gL^-1 and serum albumin concentration was 2.1 gL^-1, 1.7 gL^-1, and 1.4 gL^-1 respectively. Markedly decline (denoted by P<0.05, P≤0.01 and P≤0.001) was noticed in both the parameters concentration during acute as well as chronic toxicity, when compared with control group concentration, indicating negatively impinge of atrazine on grass carp as well as atrazine present in aquatic bodies must jeopardize the health of other aquatic fauna.