Wear affects shape and size of the friction stir welding (FSW) tool, and leads to unexpected weld properties and shorter tool life. Understanding wear mechanisms during FSW is important to prevent or reduce tool wear and ensure longer tool life for joining of high melting point metallic (HMPM) materials. Severe tool wear is a consequence of extreme thermo-mechanical environment around the tool during welding. The macroscopic and microscopic investigations of wear mechanism are conducted by performing 3D profilometer and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Analysis of the scratch formation on the tool surface is used to ascertain the presence of abrasive wear mechanism. Adhesive wear is confirmed by investigating the tool–workpiece interface layer, which features diffusion of copper. This understanding of tool wear mechanism during FSW of high melting point metallic materials will enable selection of better tool materials and improved weld properties.