Rivers play an important role in the economy and agriculture, but climate change and improper management have affected these resources. In order to better manage rivers, it is necessary to know their discharge trend and the factors that create the trend. The severe decrease in rainfall and the resulting dry periods have many negative effects on water resources. The continuation of droughts is a consequence of climate change. This study investigates rainfall and discharge changes in the Aras catchment located in the northwest of Iran. For this purpose, after data validation, 9 hydrometric stations and 5 rain gauging stations were selected with the statistical period of 1987-2016. The purpose of this study was to evaluate the trend of time series variations of precipitation and discharge variables using Mann-Kendall and Sen’s slope estimator tests. The results of the trend analysis showed that precipitation at two stations increased, however other stations did not experience any trends. Furthermore, there has been a downward trend in the discharge trend analysis at the six stations and no trends in the other three stations.