The terrigenous material of the flysch of the Pelagonian zone s.l. of the Internal Hellenides in Pelion, Skopelos, Euboea, Othrys Mountain and Argolis have been characterized by their heavy mineral assemblages, based on 114 samples. The terrigenous input can be divided into a garnet-dominated association, restricted to flysch sediments of both western Othrys and Ligourion (Argolis), and assemblages with variable amounts of the stable ZTR group (zircon, tourmaline, rutile) and apatite, found at all the other localities. The garnet assemblage is assumed to have been derived from mica schist complexes existing at the western margin of the Pelagonian microcontinent, tectonically active due to the closure of the Pindos Ocean. The situation is similar to that already known from the Pindos and Parnassos-Ghiona zones. Blue amphiboles detected in western Othrys witness the existence of blueschist terrains. The ZTR-apatite group points to a different source province, not connected regionally with the former source. The activity of this source terrain can be related to the closure of a Neotethyan ocean in the Vardar zone, along the eastern margin of the Pelagonian unit, during the early Tertiary. The heavy mineral assemblages indicate that in this source area ophiolitic complexes are tectonically incorporated to a lesser extent. Blueschists seem to be absent, as no detrital blue amphibole was found.