Phreatic events may represent precursors of magmatic eruptions, but they can also occur as single or multiple episodes punctuating the activity of volcanoes characterised by active hydrothermal systems. The Breccia De Fiore deposit represents evidence of the phreatic activity preceding by fifteen years the onset of the 1888–1890 magmatic eruption at La Fossa di Vulcano. This study integrates historical chronicles, sedimentological, physical, petrological, and geochemical descriptions of the deposit, together with 3D numerical simulations to reconstruct eruption dynamics. This study also highlights the potential impact of such relatively small phreatic explosions on the Vulcano island and the need for quantifying their hazards, especially given the proximity to populated sites and the growing tourism in this active volcanic area.