Objective: To better understand the different pathways linking socioeconomic position and HIV testing uptake in 18 sub-Saharan African countries. Design: We used cross-sectional population-based surveys between 2010 and 2018. Methods: Using a potential outcomes framework and the product method, we decomposed the total effect linking wealth and recent (<12 months) HIV testing into direct effects, and indirect effects, via internal (related to individual's ability to perceive need for and to seek care) or external (ability to reach, pay for and engage in healthcare) mediators to calculate the proportion mediated (PM) by each mediator. Results: High levels of inequalities were observed in nine and 15 countries among women and men, respectively. The mediator indirect effect varied greatly across countries. The PM tended to be higher for internal than for external mediators. For instance, among women, HIV-related knowledge was estimated to mediate up to 12.1% of inequalities in Côte d’Ivoire; and up to 31.5% for positive attitudes towards people with HIV (PWH) in Senegal. For the four external mediators, the PM was systematically below 7%. Similar findings were found when repeating analyses on men for the internal mediators, with higher PM by attitudes towards PWH (up to 39.9% in Senegal). Conclusions: Our findings suggest that wealth-related inequalities in HIV testing may be mediated by internal more than external characteristics, with important variability across countries. Overall, the important heterogeneities in the pathways of wealth-related inequalities in HIV testing illustrate that addressing inequalities requires tailored efforts and upstream interventions.