BACKGROUND There are many scientific studies on performance of different sweet potato varieties under water deficits, however, no study on Koganesengan and Beniazuma varieties has been found in the literature. This study was aimed to investigate the effects of water deficit levels (control‐WD0, low‐WD25, medium‐WD50 and high‐WD75 water deficit levels) on growth, yield and quality parameters, water use efficiency and water‐yield response factor values of these sweet potato varieties under drip irrigation. RESULTS The seasonal water consumptions of varieties were calculated as 808 and 826 mm, respectively, under no water deficit. All of the growth (except average tuber length for Koganesengan) and yield parameters of both varieties were significantly affected by water deficit treatments. However, most of the quality parameters including total dry mater, starch, ß‐carotene, ascorbic acid, protein, saccharose and glucose contents for both varieties; total ash, crude fiber and phenolic matter content for Beniazuma; and fructose content and antioxidant activity for Koganesengan variety had no response to water deficits at any level. Under high deficit and control, fresh and dry vine, tuber and total yields ranged from 4.80 to 14.54, 0.85 to 2.35, 1.59 to 10.97 and 6.40 to 25.52 t ha−1 for Koganesengan and 6.05 to 27.88, 0.99 to 4.09, 2.17 to 22.91 and 8.22 to 50.79 t ha−1 for Beniazuma, respectively. CONCLUSION The results showed that Beniazuma variety is proportionally more sensitive to water deficit than Koganesengan. It can be concluded that both varieties can be grown in Mediterranean conditions by providing optimum irrigation applications. © 2020 Society of Chemical Industry