This study adopted a qualitative technique to examine the effect of corporate governance on the capital structure of non-financial firms in developing countries from 2011 to 2022. The study reviewed thematically evidence from 50 previous studies that examined the effect of board size on leverage. The study demonstrates an inconsistent outcome, with 52 per cent of findings positive, 32 negative and 17 mixed results. The study also found that adopting a single theory is insufficient to explain the rationale of the relationships between corporate governance and capital structure. While most studies adopted secondary data, future studies may focus on using primary data and other methods instead of regression or multiple regression analysis.