Friction stir welding (FSW) and friction stir spot welding are solid state joining processes employed for the joining of similar and dissimilar materials. The processes are used by many researchers; because these processes produce sound welds; and they do not have common welding problems, such as solidification and liquefaction cracking related to the fusion welding methods. FSW and FSSW of similar aluminium and copper gained ground in the development of solid state joining processes. It may be observed that for FSW and FSSW of similar copper, many research studies were carried out using pure copper as the parent material. Whereas, for similar aluminium, almost the entire aluminium alloy series is utilized. Good quality joints with enhanced properties have been produced; and more studies are required, in order to fully optimize these processes. This could be beneficial in curbing global warming; since FSW and FSSW are both labelled as being environmentally friendly joining processes. In this chapter, FSW and FSSW research studies on similar aluminium and copper are briefly summarized in terms of the process parameters, the microstructural evolution and the mechanical properties.