This work shows the presence of zeolites in the Cretaceous Cayo formation in Coastal Ecuador. In the area of Guayaquil the Cayo formation consist of marine pyroclastic flow deposits, associated fallout tuffs and epiclastic rocks. The main zeolites are Ca-heulandite (mean Si/Al: 3.30) and Ca-clinoptilolite (mean Si/Al: 4.35). Less common are laumontite, mordenite and analcime. Zeolites compose 10–60% of the rocks. The deposit is of great importance for Ecuador, considering its enormous zeolitised outcrop area (more than 10,000 km2).