Our study aimed to evaluate the effect of trace element pollution in the polychaete Perinereis cultrifera (Grube, 1840) from two Tunisian coasts (the port of Rades, S1; and the Punic port of Carthage, S2). To this end, we used an approach based on proximate composition, biomarker responses and trace element bioaccumulation. Our results showed a decreasing order of metals concentrations (Zn>Cu>Cd>Pb) in P. cultrifera from S1 and S2. The accumulation of Cd, Cu and Zn was significantly higher in S1 than in S2, especially in summer. Lipid, protein and glycogen content also changed significantly between S1 and S2 in relation to trace metal accumulation and environmental conditions. The results revealed a higher level of thiobarbituric acid in P. cultrifera from S1 than from S2. In addition, the enzymatic and non-enzymatic antioxidant defence system (catalase, glutathione-S-transferase, superoxide dismutase, glutathione and metallothionein) was enhanced and acetylcholinesterase activities decreased in P. cultrifera in S1 in comparison with S2. A principal component analysis showed that P. cultrifera from S1 exhibited a clear disruption of oxidative stress responses and trace element bioaccumulation among seasons. Overall, these findings revealed the sensitivity of those organisms to environmental conditions.