This paper documents a Miocene littoral boulder mass at Polopos, in southern Spain. The boulder mass overlies Paleozoic‐Mesozoic schist and dolomite basement rocks, and is representative of a basin‐wide Messinian transgressive episode. The boulder mass consists predominantly of dolomite boulders which were colonized by rock‐borers. The rock‐boring community is limited to the ichnotaxaEntobiaandGastrochaenolites, the first colonizers of a mobile substrate. Two colonization intervals may be recognised in the boulder mass. The oldest of these is represented by a dolomite boulder conglomerate in which over 62 percent of the clasts haveGastrochaenolitesandEntobiaborings on their lower surface alone. The younger interval is recorded by large dolomite boulders, with mostly large diameterGastrochaenolitesborings on their upper surfaces. These borings provide an insight into the evolution of the Miocene transgressive episode in the Sorbas Basin, and into the ecology of a substrate under high ambient energy levels.