The pathogenicity of Pseudomonas sp. on the length-weight relationship and hematology of the cultured fish Cyprinus carpio were addressed in the current study. Fish samples were intraperitoneally injected with an experimental bacterial solution, containing 2.0 ×10⁶ CFU/ml at a dosage of 0.2ml. Significant behavioral changes were detected in the infected fishes, as well as a reduction in length and a loss in body weight. The results reveal that the controlled fish have a significant increase in length and weight, but the infected fish exhibit no significant growth at subsequent time intervals of the experiment. The CFs from infected populations were less than 1.0, suggesting that the fish population has not achieved its expected growth. The hematological data, such as hemoglobin (Hb) concentration, total erythrocyte count (RBC), total leucocyte count (WBC), hematocrit, packed cell volume (PCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV) were analyzed. The findings showed that while the number of WBC rises, the hematological parameters (Hb, RBC, and PCV) exhibited a substantial drop in the count with regard to a time interval of infection. Thus, the study showed that Pseudomonas affected the infected host fish's development, hematology and behavioral changes in the cultured host fish.