Breast tumour detection using flexible wearable antenna system presented in this paper removes the need for liquid coupling mediums used in conventional systems, leading to a simpler and cost effective imaging device. This is achieved by considering a planar microstrip antenna design on a flexible substrate and optimising the antenna for the skin contact operation. It is shown that systems with a matched coupling medium still have 20% theoretical reflection loss at the skin, which is eliminated in the presented system. Simulation results show three-fold increase in the current densities and electric fields in the tumour. Experimental results with in-house breast and tumour phantoms show that the received signal from a tumour has 33 dB maximum and 19 dB average (over 400 MHz range) amplitude above noise level. Theoretical analysis, simulation models, and experimental results for breast tumour detection using flexible wearable antenna system are presented and discussed.