Lithium-ion batteries have become the dominating technology for rechargeable batteries. However, they are associated with several social sustainability concerns. In particular, these concerns have been expressed for lithium-ion batteries that contain cobalt in the cathode, such as nickel-manganese-cobalt (NMC) batteries. Cobalt has been on the European Union’s list of critical raw materials since its first appearance in 2011. While not counted among the conflict minerals, the extraction and refining of cobalt in the Democratic Republic of the Congo (DRC) accounts for 70% of the global supply. Reports from this extraction include harsh working conditions, high presence of child laborers and forced evictions, particularly for the 20% share of the extraction conducted at small scale. In this work, the life-cycle health impacts of an NMC battery are quantified using the disability-adjusted life years (DALY) indicator. Health impacts from emissions are included, as well as health impacts from occupational accidents during small-scale cobalt extraction in the DRC and other processes. Two scenarios for occupational fatalities in small-scale cobalt extraction in the DRC were tested: one expert estimate at 2000 fatalities/years and one at only 65 fatalities/year based on reports in media. The results show that given 2000 fatalities/year, cobalt extraction and refining account for 18% of the total health impacts. However, the nickel in the cathode accounts for 30% and the copper used as a current collector for the anode accounts for 20%. Consequently, the results from this study show that while cobalt contributes notably to the health impacts of an NMC battery, nickel and copper are also important to consider for reducing health impacts. The main recommendations are to reduce emissions from nickel and copper extraction, to increase the share of recycled metals in lithium-ion batteries and to improve the occupational safety in small-scale cobalt extraction in the DRC.