Microwave ablation (MWA) is one of the emerging technologies in the treatment of liver, lung, prostate and breast cancers. This study is aimed at simulating an appropriate frequency for breast cancer ablation with a suitable microwave antenna. The antennas for breast cancer MWA were designed using the Finite Element Method (FEM) software in COMSOL MULTIPHYSICS version 4.4. A total number of four antenna types were designed and simulated of which 3 of the antennas were selected based on the variation in their reflection coefficient, total power density and Specific Absorption Ratio. The result shows that frequency affects power dissipation into the breast tissue. Compromising between power dissipation, reflection coefficient and diameter of necrotic tissue, simulated monopole antenna with radiating length 8mm operating at 6.61 GHz produced better and efficient power dissipation into the breast tissue. Such suitable frequency is significant to meet the dielectric property of the tissue (breast) needed to achieve a better coagulation zone with minimal injury to surrounding normal tissues or cells.