The use of small hydrocyclones for the separation of particles in the micron range is of growing interest. However, these hydrocyclones are typically limited to conventional shapes or restricted to specific outlet sizes, which can lead to sub-optimal performance. The aim of this study is to present a method for the optimisation of small hydrocyclone design. This method consists of four steps that combine designing, Computational Fluid Dynamics (CFD) simulations, 3D printing and experimental testing. A 3D printed 10 mm hydrocyclone was shown first to match the performance of a ceramic equivalent, followed by factorial experiments with a set of printed hydrocyclones of different spigot and vortex finder diameters. A CFD model for small hydrocyclones was implemented and, following validation with the experimental data, used to simulate small hydrocyclone designs with parabolic walls. The model predicted improved separation performance compared to the conventional conic wall designs. In a novel development, a 10 mm hydrocyclone with parabolic walls was 3D printed and the prediction confirmed experimentally. The solids recovery and concentration ratio were increased by 10 percentage points and 0.2, respectively, for a 0.5 g/L yeast suspension and at an equivalent pressure drop. The use of 3D printing to manufacture small hydrocyclones of various designs has been proven in this study to be practical and to allow rapid prototyping design informed by CFD simulations. This is a significant improvement in the cost, time and versatility associated to hydrocyclone design and can lead to enhanced separation performance.