Groundwater irrigation is essential for agriculture, especially in arid and semi-arid regions. This study examines the water-energy-carbon nexus (WECN) of groundwater-irrigated agriculture in Razavi Khorasan, Iran, analyzing data from over 10,000 registered wells. It evaluates energy efficiency, energy intensity (EI), and associated carbon emissions across different irrigation methods and pumping technologies. Results indicate that 88.4 % of wells are powered by electricity, with an average EI of 1.42 kWh/m3 and a pumping efficiency of 27.8 %. Drip irrigation increases energy consumption by 5.2 % (1.62 kWh/m3) compared to flood irrigation (1.54 kWh/m3), primarily due to pressure losses in tubes and the irrigation system layout. Submersible pumps show a 13.7 % lower EI (1.45 kWh/m3) and a 14 % higher efficiency (28.5 %) compared to shaft and sleeve (vertical pumping) systems. Carbon emissions per cubic meter of water withdrawn are calculated as 759.3 gCO2/m3 for electric wells and 339.8 gCO2/m3 for diesel wells, highlighting the environmental inefficiency of the electric grid. Total carbon emissions from groundwater irrigation in Iran are estimated at 18.01-18.99 million metric tons, accounting for 2.53 %-2.67 % of Iran's total emissions. The findings of this study provide policymakers with valuable insights to make informed decisions on groundwater irrigation, addressing the challenges of water scarcity, carbon emissions, and sustainable agricultural practices in similar regions worldwide.