Abstarct: The Kashmar basin is located in the Khorasan-Razavi province at Central Iran. The Kashmar aquifer covers an area of approximately 7600 km2. This research examines the quantity and quality of the Kashmar aquifer. Groundwater in the Kashmar aquifer is used for various purposes such as drinking, industrial, and agricultural uses. Due to the unregulated use of groundwater, the water level has experienced a severe decline. The direction of groundwater flow in the Kashmar aquifer is from east and northeast towards the southwest. The representative hydrograph of the aquifer has been plotted for a 10-year period, showing an annual decline rate of about 0.84 meters. The groundwater balance for the Kashmar aquifer has been calculated, indicating an input of 42.92 million cubic meters and an output of 63.126 million cubic meters (MCM). The total extraction from the aquifer exceeds the total inputs, resulting in a negative balance and reservoir depletion of around 35 MCM, leading to a decline in the water table. Proper management and optimal use of groundwater can help to replenish the reservoir. Furthermore, the analysis of the Kashmar aquifer water quality shows variations in electrical conductivity and different salts at various points. The higher the decline in the water table, the lower the quality of groundwater will be. The dominant water type in the Kashmar aquifer is Na-Cl.