Anabas testudineus is a commercially important and nutritionally rich fish. This investigation evaluated haemato-biochemical responses of Anabas testudineus associated with exposure of sublethal concentrations 3.275 ppm (1/2th of LC50) and 1.31 ppm (1/5th of LC50) of diazinon 60 EC under laboratory conditions for one week (7 days), two weeks (14 days) and four weeks (28 days). Increase exposure time and dose lead to decrease of Hemoglobin (Hb), Total Erythrocyte Count (TEC) and Hematocrit (HCT) values, but increase of Total Leucocytes Count (TLC), Mean Corpuscular Hemoglobin Concentration (MCHC) and Mean Corpuscular Hemoglobin (MCH) values in both sexes. Significant (P<0.01) increase in blood glucose (77.44 mg/dl) and cholesterol (232.03 mg/dl) level was more noticed among female whereas total protein contents were significantly decreased. Three factors ANOVA analysis showed significant (p<0.01) variation in TLC (F=5.56), MCV (F=20.445), MCHC (F=12.427), glucose (F=4.029) and cholesterol (F=5.008). Sublethal concentrations of diazinon lead to subtle changes in blood indices of test fish. ANOVA showed that the pesticide concentrations had more influence than the duration of exposure in all cases (P<0.01). Findings of this study showed sex-related and depicted severity of diazinon was both dose and duration dependant.