Brain tumors is a common cause of death worldwide. It may be difficult to detect a brain tumor at an early stage due to its small size as well as some other drawbacks of the methods used for detection. In this paper, a proposed rectangular microstrip patch antenna with Defect Ground Structure (DGS) operating in the X-band around 5 GHz was developed for tumor detec-tion. The antenna was designed with dimensions of 23.72×29.78×1.588 mm3 and a Roger-RT /5880 (εr=2.2) substrate material and a rectangular feed-line was used to supply the antenna's radiating patch. The design dealt with a single element and an array of elements in order to im-prove performance compared to previously published research. The antenna's effectiveness was evaluated by applying it to a brain phantom with and without a tumor. The dimensions of the antennas are optimised to effectively identify different localized tumours with a minimum radius of 5 mm while also taking into account special safety issues to be less than 1.6 W/Kg for a 1g cube-shaped tissue.