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Abstract. Given the short span of instrumental precipitationrecords in the South American Altiplano, longer-term hydroclimatic recordsare needed to understand the nature of climate variability and to improvethe predictability of precipitation, a key natural resource for thesocioeconomic development in the Altiplano and adjacent arid lowlands. Inthis region grows Polylepis tarapacana, a long-lived tree species that is very sensitive tohydroclimatic changes and has been widely used for tree-ring studies in thecentral and southern Altiplano. However, in the northern sector of thePeruvian and Chilean Altiplano (16–19∘ S)still exists a gap of high-resolution hydroclimatic data based on tree-ringrecords. Our study provides an overview of the temporal evolution of thelate-spring–mid-summer precipitation for the period 1625–2013 CE at thenorthern South American Altiplano, allowing for the identification of wet ordry periods based on a regional reconstruction from three P. tarapacana chronologies. Anincrease in the occurrence of extreme dry events, together with a decreasingtrend in the reconstructed precipitation, has been recorded since the 1970sin the northern Altiplano within the context of the last ∼4 centuries. The average precipitation over the last 17 years stands outas the driest in our 389-year reconstruction. We reveal a temporal andspatial synchrony across the Altiplano region of dry conditions since themid-1970s. Independent tree-ring-based hydroclimate reconstructions andseveral paleoclimatic records based on other proxies available for thetropical Andes record this synchrony. The influence of El Niño–SouthernOscillation (ENSO) on the northern Altiplano precipitation was detected byour rainfall reconstruction that showed past drier conditions in our studyregion associated with ENSO warm events. The spectral properties of therainfall reconstruction showed strong imprints of ENSO variability atdecadal, sub-decadal, and inter-annual timescales, in particular from thePacific NIÑO 3 sector. Overall, the recent reduction in precipitation incomparison with previous centuries, the increase in extreme dry events andthe coupling between precipitation and ENSO variability reported by thiswork is essential information in the context of the growing demand for waterresources in the Altiplano. This study will contribute to a betterunderstanding of the vulnerability and resilience of the region to theprojected evapotranspiration increase for the 21st century associated withglobal warming.