Synthetic diamond competes with the conventional cemented carbide (WC-Co) tool material in some applications due to its extreme hardness. However, so far, these materials have not been compared from a life cycle perspective regarding their environmental and resource impacts. The aims of this study are i) to provide detailed life cycle assessment (LCA) results for industrial polycrystalline diamond (PCD) production from diamond grit produced via high-pressure high-temperature (HPHT) synthesis and ii) to conduct the first comparative LCA of PCD and WC-Co tools for the cases of wood working and titanium alloys machining. The results show that the main hotspot in HPHT synthesis of diamond grit, which is the main precursor to PCD, is the use of WC-Co in the high-pressure apparatus. In PCD tool production, the electricity input and the use of tungsten and molybdenum contribute the most to environmental and resource impacts. The environmental and resource impacts of the PCD tool production can be reduced with 53-83% if solar electricity and full WC-Co recycling is applied. The comparison shows high environmental and resource improvements when substituting WC-Co tools with PCD tools in wood working, but not in titanium alloys machining.