Streamflow in the upper Yellow River Basin is affected by both climate changes and human activities. Precipitation has a bigger impact on streamflow than evaporation. Climate has a weak effect on streamflow at Jimai station but a strong effect at Lanzhou station. Human activities contribute to about 40% of streamflow changes in the basin, with stronger effects at Lanzhou station compared to Tangnaihai station. Both climate variability and human activities play significant roles in altering streamflow in the upper Yellow River Basin.