How do sub-Saharan presidents form and manage their cabinets? Previous research on intra-executive relations has focused predominantly on patterns of patronage. Although informal mechanisms remain relevant in the policy-making process, formal institutions have gained in importance in sub-Saharan Africa since the early 1990s. However, little is known about the link between presidents’ constitutional power and their decisions to appoint, remove and reshuffle ministers. This article addresses this gap by analysing the impact of presidential power on three ministerial-level variables: ethnic cabinet composition, cabinet size and ministerial stability. Based on a framework combining formal and informal institutions, we argue that presidents use formal cabinet roles and relationships to employ informal power-sharing strategies. To capture presidential power, we construct a new index of eight powers specifically related to the presidential-ministerial relationship. The theoretical model is tested with a new dataset of 41 sub-Saharan African countries from 1990 to 2016. OLS regressions show that presidents with greater constitutional power form ethnically exclusive cabinets, increase cabinet size and raise minister stability, albeit the latter effect is not statistically significant. These findings shed new light on the impact of different institutional designs on intra-executive processes in general and, in particular, on presidential actions vis-à-vis cabinet ministers in sub-Saharan Africa.