Extreme precipitation events represent significant climate hazards with substantial impacts on agriculture and water resources. This study aims to investigate the trends of extreme precipitation indices (CDD, CWD, R95P, R99P, and PRCPTOT) in the Helleh River Basin and analyze their relationship with teleconnection patterns (NAO, MJO, MEI, and IOD) during the 2000–2022 period. The trends of these indices were evaluated using the Mann-Kendall test, while the relationships with teleconnection patterns were assessed through correlation and multiple regression analysis (with three- and six-month lags). The results indicate that most extreme precipitation indices exhibited a decreasing trend during this period, which was statistically significant at several stations. Among the teleconnection patterns, the North Atlantic Oscillation (NAO) demonstrated the most significant influence on the duration of dry and wet periods. Conversely, the Madden-Julian Oscillation (MJO) showed a negative and significant relationship with total annual precipitation across all stations. The impacts of the Multivariate ENSO Index (MEI) and the Indian Ocean Dipole (IOD) were generally insignificant and confined to specific stations and indices; however, a six-month lag of the IOD showed a significantly stronger influence on CDD in Bushehr compared to the concurrent relationship. These findings emphasize the necessity of incorporating teleconnection patterns, particularly the NAO and MJO, into climate forecasting and water resource management strategies for the Helleh Basin.