Bisphenol A (BPA) is an endocrine disruptor, widespread into the marine environment, which can be accumulated in marine organisms, representing a serious threat to human health, even if it is present at low concentrations. This study presents a new methodology for detecting BPA in the edible mussel Mytilus galloprovincialis which, compared to the existing ones, has several advantages. It is cheaper, faster, independent of the amount of organism material considered, and can be used even for the analysis of very small samples: LOD of 0.13 μg g-1 was obtained extracting 50 mg of tissue. The detection of BPA was obtained by means of a tailored method able to spot the contaminant spiked or bioaccumulated by living mussels at different concentrations and time points. Under environmental conditions inedible mussels (not depurated) bioaccumulated up to 0.6 μg g-1 (d.w.). Our methodology was applied to in vivo experiments whereas the concentration of BPA detected in mussels' tissues was found to depend on the quantity administered. This methodology may provide the baseline for future research and improve environmental regulation and risk assessment protocols.