The nitrogen (N) cycle and N balance have primarily been modified by anthropogenic activities and environmental changes at various scales, including biological individual, ecosystem, local landscape, continental region, and global. These modifications have drastically affected the structures and functions of natural and agricultural ecosystems in terrestrial and aquatic areas. In this manuscript, we first present a modified view of the global N cycle that includes N transport, conversion, and exchange processes. Second, several crucial issues concerning N balance, including N deposition and excessive addition and the dynamics of N and other nutrients, are reviewed. Third, the effects of climate change factors, including water status, warming, and elevated CO₂ concentrations, on N balance and the N cycle and their interactions within and with other environmental factors are outlined. Finally, intervention strategies for improving N balance and N cycling to address rapid continual climatic change and socio-economic development are presented and discussed. It is highlighted that the altered N balance and N cycle between the geosphere, biosphere, and atmosphere have produced the profoundly critical challenge of maintaining N levels within an appropriate range, which should be considered by relevant people and sectors, including researchers, managers, and policy makers from ecological, environmental, and sustainable development sectors.