The drift capacity of unreinforced masonry walls plays a relevant role in both the assessment of existing structures and the seismic design of masonry buildings. Eurocode Part 1–1 now incorporates guidelines for considering inelastic behavior, where the deformation capacity is a necessary variable. The procedure requires the employment of empirical drift capacity models, but they rely on limited experimental data, often lacking consideration for the effect of wall size. The use of reduced size walls while keeping brick dimensions is a common practice in experimental works. However, no fixed lower bound limits have been set yet. This paper presents findings from an experimental study on how wall size influences URM wall drift capacity. Six quasi-static cyclic tests were conducted on walls of varying heights (2.8 m, 2.0 m, and 1.4 m) and compression loads. All had an aspect ratio (Lw/Hw) of 0.77 and were subject to double bending boundary conditions to observe shear-controlled behavior. The study identifies key mechanical phenomena affecting size effects, significant for enhancing analytical models, and provides valuable data for validating numerical studies. These findings offer significant contributions to understanding the size effect in URM walls and establish guidelines for conducting tests on smaller specimens to obtain drift capacity values for storey-high walls.