AbstractTo determine if the uniconazole concentration(s) whether could enhance the cadmium (Cd) tolerance of Cyphomandra betacea seedlings, the effects of spray treatments with various uniconazole concentrations (0, 5, 10, 20, and 50 mg/L) on the physiological characteristics and Cd accumulation of C. betacea seedlings were studied in a hydroponic experiment. The results indicated that uniconazole significantly decreased the Cd content of C. betacea seedling stems, leaves, and shoots, but significantly increased the biomass of all analyzed seedling parts. Additionally, the leaf chlorophyll a, chlorophyll b, and carotenoid contents as well as the net photosynthetic rate, transpiration rate, stomatal conductance, and CO2 concentration of intercellular were higher for the uniconazole‐treated C. betacea seedlings than for the control seedlings. The optimal uniconazole concentration significantly promoted the superoxide dismutase, peroxidase, and catalase activities and the soluble protein content of C. betacea leaves. Moreover, uniconazole decreased the soluble sugar content of the C. betacea roots and stems, but had the opposite effect on the soluble sugar content of the leaves and shoots. The 20 mg/L uniconazole treatment resulted in the highest C. betacea seedling biomass and the lowest Cd content, indicating this concentration may be useful for improving C. betacea seedling growth in Cd‐contaminated soils.