In this study, an efficient near-field imaging system using miniaturised bowtie antennas is proposed for the three-dimensional (3D) detection of breast tumours. To ensure good penetration and high resolution, a novel compact bowtie antenna is developed. The antenna features a high fractional bandwidth covering both low and high frequencies, while still small in size. A hemispherical array of 16 compact bowtie antennas is built and following a multistatic scenario, scattered signals from two breast phantoms with one and two embedded tumours inside are recorded. The radar-based set-up operates in the frequency range of 1.2–7 GHz. It is shown that the imaging system can successfully detect the tumour phantoms in 3D space.