While lichens are vital for ecosystem processes and serve as useful bioindicators, lichen diversity remains understudied, particularly in southern Ecuador. Here, we report the first inventory of corticolous (on tree bark) lichens in the Pachicutza watershed, Zamora-Chinchipe, Ecuador, in the Amazonian region. We conducted a random survey across the understory of the forest, without predefined sampling units (40 trees were sampled within a 2500 m² area). A total of 30 lichen species from 19 families were recorded, with the most frequent species in the Parmeliaceae and Roccellaceae. Additional noteworthy species were identified in the Graphidaceae, Trypetheliaceae, and Pyrenulaceae. This small sampling revealed a diversity of lichens in the Pachicutza watershed, which should be protected as a reservoir of biodiversity. Although the area is currently well-preserved, the increasing pressures of mining and deforestation in the region underscore the need for monitoring ecological integrity. Future research should explore new molecular approaches for characterizing lichen diversity, which have implications for assessing the impact of anthropogenic activities on these ecosystems. Keywords: Amazonian Forest, bioindicators, Crustose lichens, Graphidaceae, lichenized fungi, Parmeliaceae.