Aggregation and sedimentation of fine particles are commonly encountered phenomena in mineral processing as well as in many other industrial processes. Previous computer models tend to concentrate on certain aspects of either aggregation or sedimentation but not on both at the same time, even though the two processes often take place simultaneously. This paper describes an integrated random walks based model in an attempt to ‘fill the gap’. The main features of the model include the ability to simulate aggregation, breakage and internal re-arrangement of aggregates; to allow aggregation and sedimentation to take place simultaneously; to allow conditions (e.g. particle concentration) to change either gradually or suddenly during the simulation; and to have multiple components where each component may behave differently from another. Simple comparison with some available experimental results is presented to demonstrate the versatility of the simulation program. Potential applications and future developments are also discussed.