Magnetron sputtered non-hydrogenated diamond-like carbon (DLC) coatings were tested against Al, Cu and Ti pins using a vacuum pin-on-disc tribometer. The objective was to compare Al, Ti, and Cu transfer to DLC coatings in air (29% RH) and an inert atmosphere (argon). In argon, a significant amount of adhesion and material transfer occurred from the Al and Ti pins to the DLC coating surfaces inflicting severe damage to the coatings. Wear and material transfer of the DLC coating against Cu were negligible in argon. Compared to tests in argon, the tribological performance of the DLC coatings against Al and Ti improved significantly in ambient air. In contrast, the wear rate of the DLC coatings against Cu was much higher in ambient air compared to that in argon.