A miniaturized metasurface antenna using capacitive loading is investigated. First, anovel miniaturized metasurface unit cell is proposed. By introducing a pair of capacitive-loading strips inserted along the diagonal of a square patch, a size reduction of 55% can be achieved for this miniaturized unit cell. Furthermore, a compact metasurface antenna of a 4×4 array is designed using the miniaturized unit cells, which is fed by a slot structure. The radiation mechanism of the metasurface antenna is revealed and explained using a characteristic mode analysis (CMA). To validate the design, a prototype of the proposed antenna is fabricated and measurements are taken. The measured -10 dB impedance bandwidthis 21.7%, while a gain of 6 dBi is observed within the operating bandwidth.