Abstract Cloud condensation nuclei (CCN) modulate the properties and thus the climate effects of clouds. The North African dust plume is an important source of CCN in the North Atlantic trade‐wind zone. Yet, research into the nature and sources of these CCN is sparse, making it difficult to fully assess related cloud effects. Using combined airborne in situ measurements with aerosol modeling we show that ≥60% of CCN in the dust plume were not mineral dust, but co‐transported sulfate particles. We estimate the contribution of anthropogenic sulfur emissions to this particulate sulfate to be 50%–70%. While dust plumes in general are considered natural aerosols, these numbers illustrate that at least one third—but likely more than half—of the CCN were of anthropogenic origin. This points out that even in regions where a natural aerosol absolutely dominates particle mass, a considerable anthropogenic climate impact may be present.