Nanomedicine is one of the fastest growing areas of nanotechnology. The control over nanoparticle design and the ability to tailor nanoparticle performance to fit exacting requirements is anticipated to enhance the safety and efficacy of patient treatment. Within this space, molecular polymer brushes – single macromolecules of the size of colloids – offer a modular platform to precisely engineer nanoparticles with uniform size, shape and composition. In addition, this technology permits the compartmentalisation of chemical environments to produce multifunctional nanoparticles for tailored biomedical applications. This article highlights the recent developments in polymer brush nanoparticles for use in delivery and imaging applications.