Runoff and sediment discharge have displayed great reductions due to climate change and enhanced various human activities during recent decades in the Jialing River, China, with significant environmental and social implications. The water balance equation, double mass curve, and linear regression analysis were employed to quantify the contributions of climate change and human activities to runoff and sediment discharge reductions in the Jialing River during 1960–2017. The results indicated that the annual runoff of the Jialing River exhibited a significant decreasing trend of − 2.75 × 10⁸ m³ every year (P < 0.05) but no significant abrupt change occurred, while annual sediment discharge significantly decreased by 0.03 × 10⁸ t every year (P < 0.05) with a significant abrupt change in 1990 (P < 0.05). Climate change led to a great reduction (82.2%) in annual runoff from 1960 to 2017 in the Jialing River, whereas the contribution of climate change to sediment discharge reduction in the human-affected period (1990–2017) was only 4.55% and precipitation inclined to increase sediment discharge in recent years (2010–2017). The reduced sediment discharge in the 1990s was mostly due to the implementation of soil–water conservation programs and the reduction after 2000 was due to the development of reservoirs as well as the implementation of soil–water conservation programs. The results provided references to develop various human activities better and drew great attention to strengthening basin management.