Plastic wastes are usually dumped into water that ultimately break down into microplastics (MP), which are harmful to fish populations. Thus, studies on microplastic pollution in water bodies are essential to comprehend its effects and develop practical approaches to protect aquatic life and ecosystems. The current study investigated the effects of water-borne microplastics polyethylene terephthalate (PET-MPs) on growth, hematological indices, serum biomarkers (ALP, AST, ALT, and cortisol), and oxidative status of targeted organs (liver, gills, and intestine) of commercially important fish, Labeo rohita (L. rohita). Healthy individuals of L. rohita (weight, 30 ± 2g; length, 10 ± 1 cm) were exposed to different concentrations (T₁-0, T₂-10, T₃-20, and T₄-40 mgL^-1) of PET-MPs with an average size of 546.91μm, respectively, for a period of 28 days. The results indicated the dose-dependent toxic effects of PET-MPs on growth and biochemical parameters of L. rohita. Growth performance was considerably (p≤0.05) decreased in PET-MPs exposure groups. Hematological results indicate that red blood cells, hemoglobin and hematocrit (HCT) values were significantly decreased as the concentration of PET-MPs increased. In the case of serum biomarkers, the levels of aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and cortisol were significantly increased. Likewise, antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) activities and melano dialdehyde (MDA) level were also significantly increased in an organ- and dose-dependent manner. PET microplastics caused apparent dose-related physiological stress and organ toxicity in L. rohita, which showed their adverse effects on fish health and their potential threat to aquatic ecosystems and food safety. This study could help regulatory bodies to take appropriate steps to maintain healthy conditions of water bodies.