An effort is currently being made to reduce the acid concentrations in traditional methodologies for the analysis of metals based on green chemistry. However, it becomes necessary to develop alternative extraction and analytical environmentally friendly methods that completely avoid the use of acids. In this sense, a Microwave Assisted Micellar Extraction (MAME) method was developed, which employs biodegradable surfactants as extractants. On the other hand, Posidonia oceanicahas demonstrated its potential as a bioindicator for metal pollution in the marine environment. Therefore, a new green method has been tested for the extraction of heavy metals (Ni, Cr, Cu, Pb, Cd) from Posidonia oceanica, by using a mixture of biodegradable surfactants: Sodium Dodecyl Sulphate (SDS) and Triton X-100 as extractants and analysis by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The proposed method showed, in general, satisfactory recovery percentages, RSD below 7.29%, and LOD ranging from 0.04 to 0.22 μg g−1. On the other hand, the proposed method was applied to aged Posidonia oceanicaas well as different macrophyte samples. The results obtained were compared to those from ISO 11047:1998.