Regional dryland dynamics are shaped by long-term climate and hydrological changes, yet they remain poorly understood, especially in South America. This study analyzes hydroclimatic trends in Argentine drylands (1961–2020) using temperature (TEMP) and precipitation (PRE) data from the Climatic Research Unit (CRU). Drylands were defined using the aridity index (AI) as the ratio of PRE to potential evapotranspiration (PET). Four regions were identified, and linear and nonlinear trends were analyzed. Results indicate aridification driven by declining PRE and increasing PET. PRE shows heterogeneous patterns, with declines (−4% per decade) and localized increases (0–2.5% per decade), while PET rises slightly (0–1.5% per decade). AI exhibits a negative trend, particularly in Northwest and Patagonia (−3.02 and −2.52% per decade, respectively). Nonlinear signals were observed in PRE and AI. In Northwest, Eastern Sub-Andes and Central-West, both variables increase until the late 1970s, decrease until the mid-2010s and then recover toward the present. In Patagonia, they show an initial increase followed by a sustained decline. PET shows monotonic behavior with few oscillations across all regions. These patterns suggest that PRE primarily drives aridification, while rising PET modulates its intensity.