The main aim of this study was to gather teachers' views to determine the effect size of gender differences on the instructional leadership behavior of school principals. The standardized mean difference (SMD) was calculated to measure the effect size in this study. An initial search yielded 126 studies on the research topic, which consists of master theses, doctoral theses, and conference proceedings. After a detailed inclusion process, 38 studies, having data according to coding protocol, were included in the meta-analysis. The total study sample was 15,280 teachers of which 7,236 were males and 8,044 were females. The calculated effect size (SMD) for the random effect model was "d" = 0.048 [0.001 - 0.094], which indicated with statistical significance that male teachers were favored more.