Polycrystalline Diamond (PCD) is used as a cutting tool for machining non-ferrous metals and composites, especially aluminium alloys. The use of aluminium alloys in the automotive industry is forecasted to increase by 50 % from 2020 to 2030. This implies that machining of aluminium alloys will increase significantly, and the detailed investigation of PCD degradation mechanisms and the development of PCD material and tooling solutions is a necessity for efficient and robust manufacturing processes. This research aims to study the attrition wear mechanisms in Polycrystalline Diamond tools during interaction with aluminium using both a machining test as well as simplified laboratory scale tribological test. Two grades of PCD with similar chemical composition and different diamond grain sizes (10 μm and 25 μm) were used in the experiments and the counter material was a metal matrix composite (Al + 15 vol% of SiC) in machining test and AA6082 in the tribological tests. The wear rate of the two PCD grades were similar in machining tests. The PCD grade with the larger grain size showed a rougher worn surface topography, which can be attributed to the attrition wear by larger removed grains. During the cutting process, the binder phase (Co) is more easily removed compared to the PCD grains. This weakens the mechanical anchoring of the diamond grains in the PCD microstructure. When the diamond grain loses its anchoring, it is detached from the PCD microstructure damaging the cutting tool by attrition wear. Analysis of cutting tool inserts from turning tests and tribological tests revealed two types of wear phenomena, micro-wear and macro-wear both promoted by detachment of diamond grains from the PCD tools. This confirms that attrition wear takes place during machining of aluminium alloys using PCD, and it can be replicated in a simplified laboratory test setup.