In this paper, a new behavioural mixer model is introduced. In addition to amplitude nonlinearity; phase nonlinearity and memory effect of the mixer are modelled in a multi-box structure. Each nonlinearity source is modelled in distinct blocks of which cascade connections compose the behavioural mixer model. A test-bed has been constructed including a reference mixer and through measurements, amplitude and phase characteristics of the main tones and IMD products are modelled. The proposed behavioural model delivers a good match between measured and simulation results. The mixer model may be curve fitted to the characteristics of any mixer by optimizing its variable parameters and thus can be used in modelling different types of mixers. Thus, the proposed mixer model may be used in computer simulation tools and in linearization applications.