This study addresses the increasing concern about naphthalene, a polycyclic aromatic hydrocarbon (PAH), highlighting its growing threats to the environment and aquatic life. The research examines its impact on Anabas testudineus (Bloch) through a detailed dose-specific bioenzymological analysis. Experimental fish groups were exposed to T1 (0.71 mg/L) and T2 (1.42 mg/L) naphthalene concentrations, representing 25 and 50% of the LC 50 value, respectively, over a 1−21 day period. Following the experiment, water samples underwent physicochemical analysis, while fish tissues were examined for diverse bioenzymological parameters. Among these parameters, aspirate aminotransferase (AST) and alanine aminotransferase (ALT) serve as crucial indicators for monitoring the physiological status of fish and addressing pollution induced by PAHs, especially naphthalene. Statistical significance was observed in morphopathological changes and erythrocyte alterations, particularly the presence of tear-drop appearance (Tr) positively interacting with swelled cells (Sc), vacuolated cells (Va), and sickle cells (Sk) (P < 0.05). These findings highlight tear-drop appearance (Tr) as a significant biomarker in response to naphthalene exposure. The observed changes in A. testudineus tissue bioenzymology, apoptosis, and erythrocytic alterations were exposure and dose-dependent. The research highlights the significance of overseeing and controlling PAH concentrations in aquatic ecosystems to ensure the well-being of A. testudineus (Bloch).