ABSTRACT: In this study, we report the results of litho- and biostratigraphic analyses made in the mildly metamorphosed Paleozoic succession of the Longi-Taormina Unit (PeloritanianMountains, southern Italy), which up to now is poorly known. Three main formations based on their litho- and biostratigraphy have been defined and proposed for the first time (from base to top):Castelmola Formation, Lower Pizzo Leo Formation, and Upper Pizzo Leo Formation. The first two formations, composed mostly of marine fine-grained siliciclastic rocks, host Upper Ordovician calc-alkaline and Silurian alkaline volcanites, respectively. The upper formation is made up primarily of Silurian-Devonian pelagic metacarbonates which have released conodonts from Ludlow and Lochkovian (delta Zone) to Emsian (kitabicus, excavatus, and nothoperbonus-inversus zones) as well as Emsian dacryoconarids. These findings are relevant as they are the oldest ever found in this sector of the Alpine Chain, and they have enabled the best andmost accurate datingmade until now. The studied Paleozoic succession proved to be an important key-site to better understand facies evolution to neighboring domains like, in particular, the Calabrian Stilo Unit or other better-known Paleozoic sequences around the western Mediterranean, like those outcropping in the Alps or in the Betic and Rifian chains.