Petroleum hydrocarbons are persistent environmental contaminants capable of inducing multi-organ toxicity following chronic exposure. This study evaluated simultaneous hepatic and renal biochemical toxicity in chickens chronically exposed to a petroleum hydrocarbon–contaminated environment. Exposed chickens (n = 12; 6- and 12-month exposure groups) were compared with unexposed controls (n = 6). Serum hepatic enzymes, protein indices, bilirubin fractions, renal biomarkers, and electrolyte profiles were determined using standard biochemical methods, and data were analyzed at p < 0.05. Significant hepatic dysfunction was observed in exposed chickens, characterized by elevated serum AST (43.92 ± 15.14 vs 13.00 ± 4.52 IU/L), ALT (25.42 ± 22.15 vs 8.17 ± 6.46 IU/L), and ALP (52.67 ± 24.37 vs 25.00 ± 13.84 IU/L) activities relative to controls. Serum albumin (53.42 ± 24.23 vs 95.50 ± 14.73 g/L) and total protein (59.00 ± 23.61 vs 91.50 ± 15.60 g/L) concentrations were significantly reduced, whereas total bilirubin levels increased (11.08 ± 4.46 vs 3.40 ± 1.67 µmol/L). Renal dysfunction was evidenced by elevated serum urea (13.40 ± 9.40 vs 2.42 ± 1.89 mmol/L) and creatinine (3.21 ± 3.34 vs 1.52 ± 1.94 mmol/L), accompanied by significant electrolyte imbalance. Chickens exposed for 12 months exhibited more severe biochemical alterations than those exposed for 6 months, indicating progressive and time-dependent toxicity. The findings demonstrate that chronic petroleum hydrocarbon exposure induces significant simultaneous hepatorenal biochemical toxicity in chickens and highlight the importance of combined hepatic and renal biomarker assessment in environmental toxicology studies.