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Ammonium (NH4+) is generated during many endogenous metabolic processes in the leaves of plants, and there is increasing evidence that ammonium transporters (AMTs) play important roles in NH4+transmembrane transport and distribution. However, the expression of different AMTgenes is tissue-type specific and their functions differ. Information about AMTgenes and their expression under different environmental conditions in flowering Chinese cabbage (Brassica campestrisL.) is currently limited. Here, we isolated and characterized an AMTgene, BcAMT1;4, in flowering Chinese cabbage. BcAMT1;4 was localized to the plasma membrane and complemented NH4+transport in NH4+uptake-deficient yeast. The highest expression levels of BcAMT1;4were detected in the flowers and leaves of flowering Chinese cabbage. The expression of BcAMT1;4was induced by nitrogen deficiency and significantly inhibited by the reapplication of NH4+(NH4Cl or NH4NO3). In contrast, when plants pre-cultured in nitrate were transferred to an NH4+nutrient solution, BcAMT1;4expression was significantly enhanced. BcAMT1;4exhibited a diurnal expression pattern, with higher expression levels during the light period than during the dark period, and a peak expression at the later stage of the light period. Knowledge of AMTgenes in flowering Chinese cabbage will lay a foundation for enhancing our understanding of the functional roles of different AMTmembers in the regulation of its growth by NH4+, as BcAMT1;4seems to play an important role in leaf NH4+transport.