Antibiotics are vital in the treatment of bacterial diseases but when released into the environment they may affect the non-target organisms that perform fundamental role in ecosystem services. In this study, the toxicity of macrolide antibiotic erythromycin (ERY) on certain haematological (Hb, Hct, RBC, WBC, MCV, MCH, and MCHC) and biochemical parameters (protein, glucose, cholesterol and triglycerides) of a freshwater fish Labeo rohita was studied after short term (96 h) and long term (35 days) exposure period at three different concentrations (10, 50 and 100 µg/L). During the short and long term exposure period ERY treated fish groups showed a significant decrease in haemoglobin (Hb), haematocrit (Hct), red blood cells (RBC) and protein content in all the concentrations; whereas white blood cells (WBC) count was increased when compare to control groups. Likewise, erythrocyte indices such as mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC) and biochemical parameters such as glucose, cholesterol and triglycerides were found to be significantly (p < 0.05) altered in ERY exposed fish compared to control groups. The present investigation conclude that ERY at 10, 50 and 100 µg/L concentration altered the haematological and biochemical parameters of fish and the alterations of these parameters can be effectively used in monitoring of the pharmaceutical compounds in the aquatic environment.