The “super-eruption” of Mt. Toba in Indonesia ∼74,000 years ago, probably the largest volcanic event witnessed by humanity, has stimulated decades of research into the eruption’s impacts on global climate and ancient human ecology. Progress has been hampered by lack of geological proxy records covering the critical time window with sufficient resolution to discern the environmental impacts directly due to the eruption. Here, we present sub-annually resolved proxy data from eastern tropical Africa which constrain the timing of the Toba eruption to Northern Hemisphere winter and suggest that it triggered modest cooling and acute drought lasting less than two years. This short-lived climate perturbation was superimposed on a multi-decadal cooling/drying trend coeval with a phase of northern high-latitude cooling characterizing the world’s transition into the last glacial period. Our findings indicate that climatic impacts of the Toba eruption in eastern Africa were modest compared with other natural climate dynamics, henceforth allowing improved parameterization of earth-system models assessing its environmental impact. Sub-annually resolved lake sediments suggest the Toba eruption caused modest cooling and drought in eastern Africa.