The purpose of this research is to analyse an alleged rock-art engraving found at Pedrógão Beach (Leiria, Portugal), by studying its geological and geomorphological context, the weathering processes of the outcrop, of the rock fragments located south of the beach, as well as the same stone slab where the assumed rock-art engraving was identified. The stone slab was found in a small cave (named Gruta da Pedra) opening in limestone south of Pedrógão beach. The study provides new data on the evolution of the site in the Quaternary and clarifies some doubts on the authenticity of the “rock-engraving”, by showing that it is actually a natural object, with no evidence of human intervention.