A substantial quantity of ballast, primarily comprising blocks and pebbles of limestones and quartzose limestones, has been recovered in Parˇzine Bay (Ilovik Island, Croatia) in the stern section of a sailing vessel discovered in 2016, that wrecked between the second and the third quarter of the 2nd C. BC. This research introduces an integrated methodology for investigating the provenance of ballast stones. Both the skeletal assemblages and the siliciclastic content of the rocks suggest a common source for most of the ballast. Micropalaeontological analyses (benthic and planktic foraminifera) and Sr87/Sr86 values indicate an age younger than 500 ka. Three main lithologies dominate the ballast rock assemblage: 1) tightly cemented quartzose grainstones and quartzarenites, 2) bioclastic quartzose grainstone with large mollusks and rhodoliths and 3) weakly indurated and bioturbated quartzose grainstone. An extensive field survey and samples analysis conducted in the Quaternary mixed carbonate-siliciclastic successions along the Adriatic and Ionian coast of Italy, reveal a very high degree of similarity between the ballast stones and the Middle to Upper Pleistocene terrace deposits of the region of Brindisi (Apulia, Italy). These similarities encompass palaeontological assemblages, age, lithofacies and microfacies associations, mineralogical composition, quartz grain morphology, sedimentary and diagenetic features, stable carbon and oxygen isotope compositions, as well as the morphology and alteration features of pebbles. Given the uniformity of the ballast of the Romano-Republican Ilovik-Parˇzine 1 wreck, the study suggests, with a reasonable degree of certainty, that it was loaded in a single operation near Brundisium, one of the major ports of the Apulian coast (Italy). The results also suggest two additional hypotheses: 1) the ballast could have served as permanent ballast transported to balance the ship after it was launched; 2) the provenance of the ballast may provide insights into the location where the ship was constructed.