An increase in foliar nitrogen isotope composition (δ
15
N) with decreasing precipitation has been shown to occur widely in non-N
2
-fixing plant species. However, similar patterns have not been identified in N
2
-fixing species. Here, we tested the relationships of foliar δ
15
N with local environmental factors and leaf properties in two leguminous shrub species (
Caragana korshinskii
and
Caragana liouana
) sampled from 30 populations. Results indicated that the mean annual precipitation (MAP) primarily accounted for the variation of foliar δ
15
N in the two species. Further analysis revealed strong negative correlations between foliar δ
15
N and MAP within and across species. These results suggest that the foliar δ
15
N of leguminous shrub species also shift along precipitation gradients, which augments our understanding of the relationships between foliar δ
15
N and climatic factors.