Although the global nitrogen (N) cycle is largely driven by soil microbes, plant root exudates can profoundly modify soil microbial communities and influence their N transformations. A detailed understanding is now beginning to emerge regarding the control that root exudates exert over two major soil N processes – nitrification and N2 fixation. We discuss recent breakthroughs in this area, including the identification of root exudates as nitrification inhibitors and as signaling compounds facilitating N-acquisition symbioses. We indicate gaps in current knowledge, including questions of how root exudates affect newly discovered microbial players and N-cycle components. A better understanding of these processes is urgent given the widespread inefficiencies in agricultural N use and their links to N pollution and climate change. Major advances in understanding the complexity of the N cycle have recently been made, with the discovery of previously unknown microbial players and N transformations. The study of plant root exudates and their influence on the plant–soil microbiome in shaping nutrient cycles has greatly intensified in recent years. Root exudates that specifically inhibit soil nitrification have been identified in important crop species, including rice, wheat, and sorghum, while others have been shown to stimulate root nodulation and N2 fixation, even in neighboring plants. By influencing soil N cycle dynamics, root exudates have been shown to improve N use efficiency and can help to mitigate environmental pollution and climate change.