This study aims at clarifying the relationship between the Cape Steno mélange, southern Andros, and the main tectonic units of the Attic-Cycladic Crystalline Belt. Jurassic protolith ages and geochemical characteristics indicate a Pelagonian affinity and point to a correlative relationship with the Tsiknias Ophiolite on Tinos Island. However, jadeitites and high-Si phengite in the gneisses clearly indicate a high-pressure metamorphic overprint that is unknown from the Tsiknias outcrop and other occurrences of the Upper Cycladic Unit. A correlation with the Cycladic Blueschist Unit (CBU) is an obvious assumption, but initially seemed difficult to reconcile with the Cretaceous protolith ages of meta-ophiolitic rocks from the CBU and distinct geochemical characteristics of associated jadeitites. The Jurassic ages of the Cape Steno rock suite either document a broader spectrum of source rocks than previously known from the CBU, or the existence of a distinct tectonic unit. We assume that the geological and tectono-metamorphic evolution of the Cape Steno occurrence is similar to that of the Makrotantalon Unit of NW Andros, which represents a Pelagonian subunit in the nappe stack of the CBU, with abundant slices of serpentinites, rare meta-gabbro and a metamorphic history comprising both Cretaceous and Eocene HP/LT episodes.