This paper presents an experimental study in high speed milling of metal matrix composites (MMCs). Machining tests were carried out on a high speed milling machine by using TiAlN coated tools and chemical vapour deposition (CVD) diamond coated tools. The cutting tool wear was investigated using an optical microscope and a scanning electron microscope (SEM). The experimental results showed that flank wear is the dominant tool wear mode and abrasive wear and adhesive wear appears to be the main wear mechanism. The build-up edge (BUE) exists during the machining process at a certain speeds. Cutting speed is a dominant factor affecting the flank wear. Generally, high cutting speed lead to severe tool wear, but there seemed to be a certain cutting speed which will cause the least tool wear. Furthermore, there exists a cutting speed limit for both TiAlN coated tools and CVD coated diamond tools in high speed milling of MMCs, beyond which the edge chipping will cause the tool failure very soon.