Comparative research on the impact of the vocational specificity of educational systems on youth labour market integration has expanded rapidly in the past decades. The present study reviews this body of research, focusing on how it has conceptualized the vocational specificity of educational systems and theorized its effect on youth labour market integration. Moreover, this study synthesizes the empirical evidence compiled in this research using a meta-analytical approach. Our review reveals that this research area is theoretically fragmented. A commonly accepted definition of the vocational specificity of educational systems is lacking and various theoretical approaches and conceptual frameworks are invoked to theorize the effect of vocational specificity, while exact mechanisms that are assumed to underlie the effect are often left unspecified. Our meta-analysis includes 105 effect estimates nested in 19 studies, published between 2003 and 2018, that used methods enabling a formal meta-analytical comparison. Results show that the overall average effect is positive and statistically significant but its magnitude is modest and there is substantial variability in the size and even direction of observed effects. We find that this variability is partly driven by which aspect of labour market integration was examined and which measure of vocational specificity was used.