Constraining the age of young lavas, which generally fall outside the effective range of traditional geochronologymethods, remains a key challenge in volcanology, limiting the development of high-resolution eruption chronologies.We present an in situ cosmogenic3He and36Cl surface-exposure chronology, alongside new minimum-limiting14Cages,documenting young eruptions at five sites in the Western Cordillera, southern Peru. Four3He-dated lavas on the NevadoCoropuna volcanic complex (hitherto thought to be dormant) indicate that the central dome cluster is young and potentiallyactive; two Holocene lavas on the easternmost dome are the youngest directly dated lavas in Peru to date. East ofCoropuna, lava domes and block-lava flows represent the most extensive output to date of Nevado Sabancaya, one ofPeru’s most active volcanoes. Two3He measurements confirm the Holocene age of these deposits and expand thechronology for one of the youngest major lava fields in Peru.36Cl surface-exposure ages from the Purupurini dome clusterand Nevado Casiri document middle-late-Holocene episodes of effusive activity, while basal14C ages from a lava-dammed wetland constrain an effusive eruption at Mina Arcata, north of Coropuna, to the late-glacial period. Thesenew data advance the recent Western Cordillera volcanic record whilst demonstrating both the considerable potentialand fundamental limitations of cosmogenic surface-exposure methods for such applications.