Mountain climate and vegetation change rapidly with altitude therefore many plant species may be found within a narrow elevation range. In mountains of northern Mongolia, a relict shrub Prunus sibirica L. occurs within restricted upland areas. We studied 25 whole-plant and leaf traits of P. sibirica at 10 locations in the Khentei Mountains. A comparison with a global plant trait variation and a path model were used to evaluate the pattern of functional response to altitude. Intraspecific variation of pigment content found in apricot was surprisely comparable to interspecific variation of terrestrial plants over a global scale. Increasing altitude caused a dramatic increase in chlorophylls and chlorophyll/carotenoid ratio and a decrease in the chlorophyll a/b. We also found a decrease in leaf thickness contributed to transpiration and water use efficiency. Photosynthetic capacity and kinetics, plant sizes, biomass were not affected by altitude. The path modelling revealed that pigment content and leaf structure were two independent ways to maintain the plant carbon and water balance. Our results identify the important role of intraspecific variation in leaf pigments and structure in plant response to altitude and we suppose that these leaf traits could be used as predictors for the species altitudinal limits.