This study investigates the dynamics and persistence of hydrological drought in the Sefidrud River Basin and examines the role of large-scale climate teleconnections in the development of prolonged dry conditions during 1958–2006. The Streamflow Drought Index (SDI) was calculated at 3-, 6-, 12-, and 24-month time scales, while the Standardized Precipitation Index (SPI) was calculated at 3-, 6-, 9-, 12-, 24-, and 48-month time scales. The Difference Integral Curve, Innovative Trend Analysis (ITA), and complementary change-point and non-parametric tests, including Pettitt, SNHT, and Mann–Whitney, were used to characterize drought variability and detect changes in the hydrological regime. The results indicate that severe climatic and hydrological drought emerged during the 1998–1999 water year—following the transition from the 1997–1998 El Niño to La Niña—coinciding with a statistically significant change point in the basin’s hydrological regime. Negative SDI and SPI values at longer time scales indicate that the basin subsequently experienced a prolonged dry phase that persisted until approximately 2006. The persistence of drought beyond short-term climatic fluctuations suggests substantial hydrological inertia and a transition toward a more persistent dry regime, potentially reinforced by land-surface feedbacks such as soil-moisture depletion and vegetation degradation. The findings further suggest that large-scale climate teleconnections, particularly ENSO and DMI, should be considered alongside regional hydroclimatic processes in drought monitoring and early-warning systems. Integrating teleconnection information with hydrological indicators may improve the anticipation of prolonged drought and support more adaptive water-resources management in the basin.