Phenotypic variation is a strategy used by some plants to cope with fluctuations in environmental factors. Ziziphus jujuba var. spinosa is widely distributed from the east coast to the inland hinterland in North China, and variations in its phenotypic traits may represent an adaptive mechanism used by this species to adapt to natural drought gradients. In order to test this hypothesis, 12 phenotypic traits of 3-year-old plants from four natural populations along an aridity gradient (Yantai, Shijiazhuang, Yinchuan, and Turpan) were examined. Variations in the phenotypic traits of Z. jujuba var. spinosa were determined by the coefficient of variation and nested analysis of variance. The results showed that (1) leaf area, leaf length, leaf perimeter, and leaf stalk length all showed decreasing trends from Yantai to Turpan, whereas an adverse trend was observed in specific leaf area; (2) as the drought gradient increased, the secondary branch length and basal diameter, bearing branch number of the secondary branch, stem-specific density, stem water content, seed mass, and length of the short axis of the seed, all decreased; and (3) the average coefficient of variation was the highest for leaf traits (33.70%) in the four populations along the natural drought gradient. This was followed by branch traits (32.41%) and seed traits (9.07%), and all the measured traits showed strong covariance. Our results suggest that high levels of variation in the aboveground morphological traits of Z. jujube var. spinosa are expressed along a drought gradient, which indicates that Z. jujube var. spinosa should be able to cope well with future climate change by exploiting effective combinations of these phenotypic variations.