Plant height is one of the key agronomic traits for improving the yield of sweet potato. Phytohormones, especially gibberellins (GAs), are crucial to regulate plant height. The enzyme 9-cis-epoxycarotenoid dioxygenase (NCED) is the key enzyme for abscisic acid (ABA) biosynthesis signalling in higher plants. However, its role in regulating plant height has not been reported to date. Here, we cloned a new NCED gene,IbNCED1, from the sweet potato cultivar Jishu26. This gene encoded the 587-amino acid polypeptide containing an NCED superfamily domain. The expression level ofIbNCED1was highest in the stem and the old tissues in the in vitro-grown and field-grown Jishu26, respectively. The expression ofIbNCED1was induced by ABA and GA3. Overexpression ofIbNCED1promoted the accumulation of ABA and inhibited the content of active GA3 and plant height and affected the expression levels of genes involved in the GA metabolic pathway. Exogenous application of GA3 could rescue the dwarf phenotype. In conclusion, we suggest thatIbNCED1regulates plant height and development by controlling the ABA and GA signalling pathways in transgenic sweet potato.