The increasing demand for sustainable alternatives to conventional plastics has propelled the interest in bioplastics. A few papers reported on the effects of plastics on crustaceans, but no indication about biodegradable polymers is available. Hippolyte inermis Leach, 1816 is a protandric shrimp commonly living on leaves of the seagrass Posidonia oceanica, in the Mediterranean Sea. This crustacean is typically chosen as a model to study sex differentiation processes. Here, we demonstrated its convenience as a model organism to study the effects of biodegradable polymers (BPs). Five BPs were studied: polybutylene succinate (PBS), polybutylene succinate-co-butylene adipate (PBSA), polycaprolactone (PCL), poly-3-hydroxybutyrates (PHB) and polylactic acid (PLA). Larvae of H. inermis were exposed to three concentrations of each BP (1, 5 and 10 mg/L, respectively) for ten days. After exposure, the expression levels of eighteen genes involved in stress response and detoxification processes, retrieved from a H. inermis transcriptomic library, were validated by Real Time qPCR. This study is the first using a molecular approach to detect H. inermis responses to contaminants and in particular to biodegradable polymers, through the evaluation of functional gene's pathways.