Reducing sensor dimension is a good way to increase system sensitivity and response. However the advantages gained must be weighed against other effects which also became significant during the scaling process. In this paper, the scaling effect of cantilever sensors from micrometre to nanometre regimes is reviewed. Changes in the physical properties such as Q-factor, Young's modulus, noise and nonlinear deflections, as well as effects on practical sensor applications such as sensor response and sensor readouts, are presented. Since cantilever is an elemental transducer and device building block, its scaling effects can be further extrapolated to other sensing systems and applications.