An ultra-wideband (UWB) antenna has been designed using high frequency simulation software (HFSS). The antenna is incorporated with metamaterial providing high gain over the UWB range, suitable for tumor detection. To substantiate the work, a hemispherical 3-D breast tissue consisting of three layers- skin, fat layer and tumor is employed. This 3-D breast structure, containing tumor is placed in between the proposed antennas, acting as transmitter and receiver which determine the reflection coefficients and transmission coefficients for both with and without tumor cases. By studying the variations in S parameters (S11 and S21) for both cases, tumor of sizes 2mm, 3mm and 4mm can be easily identified.