Serbian medieval architectural heritage is notable for its sacred architecture including numerous Christian Orthodox churches built at the territory of former Raška state during the period from the 12th to the 14th centuries. Built in the so-called Raška architectural style, characterized by overlapping features of Romanesque and Byzantine traditions, two monuments—the church of the Mother of God in Studenica monastery complex and the church of Holy Dormition in Žiča monastery complex, are exquisite sacred structures and cultural monuments of exceptional importance. They are also remarkable due to geometric-proportional regularities of their design. This paper highlights the importance of geometric concept in relation to proportional analysis of these two structures. Here presented study is conducted by two means: first one—by investigating geometric scheme with equilateral triangles, incorporated into the layout and cross section patterns of each church structure; the second one—by classical proportioning that includes proportional roots, golden section and numeric ratios.