Africa's economic and population growth prospects are likely to increase energy and water demands. This quantitative study shows that pathways towards decarbonization of the energy sector in Africa may lead to higher water withdrawals and consumption than expected. By 2065, investments in low-carbon energy infrastructure increase annual withdrawals from 1% (2.0 o C) to 2% (1.5 o C) of total renewable water resources compared to 3% in the baseline scenario, despite lower final energy demands in the mitigation scenarios. Water consumption, in comparison to the baseline, increases by 282% (2.0 o C) and 300% (1.5 o C) by 2065, due to the high water-intensity of the low-carbon energy system. To meet the 1.5 o C pathway, the energy sector requires higher water consumption overall and per unit of energy than other scenarios. These findings demonstrate the crucial role of integrated energy planning and water resources management if Africa is to achieve climate-compatible growth.