Variation in leaf morphology is an impor-tant indicator of how plants respond to different en-vironmental conditions. We analyzed the variation of morphological and functional traits of Q. petraea subsp. iberica leaf and its relationships with environmental and geographical variables across its distribution of this species to evaluate populations differentiation. The leaves of the tree were collected in diverse forest types (Ismailli, Qabala) and in arboretum (Baku) from -28 m to 900 m a.s.l., in 2017. We measured and analyzed the differentiation in morphological and functional traits of 300 leaves from 30 trees belong to three populations using univariate and multivariate methods. The morphological characteristics such as leaf size, area, widgth of leaves were measured. The results indicated that the leaf peremeter was decreased with increasing precipitation, and the values of morphological traits varied along elevation. Foliar moisture parameters (leaf mass per area, water content, relative water content, succulence) were positively correlated with annual precipitation. The precipitation was the most significant environmental factors in the variations of foliar moisture parameters and morphological traits. This study provided evidence for the adaptive plasticity-polymorphism of leaves in response to environmental changes.