Studies have noted the possibility of tax treaties constraining the tax policy autonomy of developing countries, while their impact on enterprise development within host economies remains an empirical issue. This study examines the effects and heterogeneous differences in estimated effects of tax treaties on small businesses in developing countries that agree to these agreements. The study uses the ICTD tax treaties dataset and the World Bank Enterprise Survey data to set up a quasi-experiment framework for selected African Countries. The framework compares countries’ outcomes for small businesses that ratify and enforce a tax treaty and those without a ratified tax treaty for the years pre-2005–2010 and post-2011–2019). We find that tax treaties signed and enforced by developing countries in Africa have a consistent, negative relationship with small business outcomes. These results are driven by the enterprise’s size and internationalisation status but not by the subsidiary status of the sampled small businesses. The findings have implications for policy targeted towards industrial development alongside tax treaty negotiations.