Previous studies regarding environmental impacts of nitrification inhibitors (NIs) in intensive vegetable production systems mainly focused on the fate of individual nitrogen (N) compounds. Due to the influence of various N-dynamic pathways on one another, systematic observations, taking into account all key component processes, must be carried out to achieve practically useful recommendations. As well, the mechanisms of how NI application leads to increasing vegetable yields are not well understood. Therefore, we conducted a field experiment with three leading vegetable crops (lettuce, celery, and tomato), and two urea N input rates, without (N1, N2) or with a nitrification inhibitor, 2-chloro-6-(trichloromethyl)-pyridine (CP) (N1 + CP, N2 + CP), to evaluate the comprehensive effects of CP on reactive-N emission in these intensive vegetable production systems, with a focus on leaching, ammonia (NH₃) volatilization, and nitrous oxide (N₂O) emission, and to clarify the possible mechanisms by which CP affects vegetable yield. The results show that CP application significantly decreased (p < 0.05) N leaching by 36.9, 26.9, and 28.4 %, soil residual NO₃-N contents by 34.1, 43.7, and 43.9 %, N₂O emission by 46.4, 77.2, and 36.9 %, and significantly increased (p < 0.05) NH₃ volatilization by 33.5, 56.3, and 308.1 % in the lettuce, celery, and tomato seasons, respectively, while having no significant effect on yield at the typical N-application rate (N2). Under 60 % of the typical N-application rate (N1), CP addition significantly increased (p < 0.05) yield and N-use efficiency (NUE) over the three-season period by 23.9 and 55.1 %, respectively, significantly reduced (p < 0.05) N₂O emission by 43.5 %, while having no significant effect on the other three observed N processes. In a lettuce-celery-tomato rotation, compared with the typical N-application rate (N2), 60 % of the typical N-application rate with CP addition (N1 + CP) significantly increased (p < 0.05) yield and NUE by 37.1 and 214 %, and decreased (p < 0.05) soil residual NO₃-N contents, N leaching, and N₂O emission by 70.9, 51.1, and 69.6 %, respectively, and had no significant effect on NH₃ volatilization. Furthermore, the distribution analysis of N derived from ¹⁵N-labeled urea in tomato aboveground suggested that CP application significantly decreased (p < 0.05) N allocation to stems and leaves by 12.1 and 9.7 %, and significantly increased (p < 0.05) N allocation to fruits by 31.2 %, averaged over 60 % and 100 % N treatments. Application of CP increased N storage in fruits and benefited yield.