Some nano grained Al materials were produced by mechanical milling/alloying followed by vacuum hot pressing: nano grained pure Al, Al-1.5Mg and Al-0.7Mg-1.0Cu alloys in wt%. The nano bulk materials had average grain sizes of 90-150 nm and ball-on-disk wear equipment was used to investigate the effects of grain size comparing to coarse grained pure Al and T6-treated Al 6061 alloy. In comparison of coarse and nano grained pure Al materials, nano grained specimens showed much higher wear resistance and size of wear debris was very fine as much as 100 nm at applied load of 100g. Wear in nano grained materials proceeded by micro fracturing mechanism like abrasion in low applied and sliding velocity and the mechanism resulted in high wear resistance. Nano grained Al-1.5Mg and Al-0.7Mg-1.0Cu alloys showed much superior wear characteristics due to nano grains and high hardness. As a result, size of grains was a predominant factor for high resistance at low applied load and/or sliding velocity, while hardness at higher applied load or velocity.