Understanding spatiotemporal rainfall trends in the Lake Tana Sub-Basin, Ethiopia, is crucial for agricultural planning and water resource management. Analyzing these trends helps develop effective strategies to mitigate the impacts of both high- and low-rainfall seasons. This study analyzes rainfall trends from 1991 to 2023 using Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data. Methodologically, the analysis employs the coefficie nt of variation (CV), standardized anomaly index (SAI), and standardized precipitation index (SPI). The modified Mann-Kendall trend test and Sen’s slope estimator are utilized to assess trends and magnitudes of change. Results showed that the annual rainfall CV during 1991– 2023 periods is between 7.5 and 11.5%, while the seasonal rainfall CV extends from 7–15%, 24–48%, and 25–80% for the average Kiremt (June–September), Belg (February–May), and Bega (October–January) seasons, respectively. On a monthly basis, the trends of rainfall increased in all months except in March, April, June, and August. However, the trends were statistically significant (α = 0.001) in July and September. On a seasonal basis, the trends of mean annual, Kiremt, Belg, and Bega seasons rainfall increased. while statistically significant increase in annual Kiremt at (α=0.001).The SAI values for the Lake Tana sub-basin (1991– 2023) show 3.03% of years were extremely wet, 9.09% were very wet, and 72.72% were near normal. Additionally, 12.12% of years were moderately dry, and 3.03% were severely dry. The analysis of monthly SPI shows the driest periods occurring in 1992, 1997, 2002–2007, 2009, and 2015. Conversely, excess rainfall was observed in 1998, 2008, and 2014, alongside other near-normal years, as indicated by historical monthly SPI values. Generally High spatial and temporal rainfall variability was observed at the monthly, seasonal, and annual time scales. Seasonal rainfall has higher inter-annual variability in the dry season (Bega) than other seasons. The trends in rainfall increased in most of the months. Besides, the trend of rainfall increases in the annual Kiremt, Belg, and Bega seasons. The study also indicated the occurrence of droughts in the Lake Tana sub-basin.