In this paper, a miniaturized gain-enhanced antipodal Vivaldi antenna (AVA) structure is proposed with good performance for 5G application. Its operating frequency band is extended and gain is improved at lower frequencies due to the use of gradual corrugated edges (GCE). By applying I-shape metal director (IMD) on the surface of the radiation aperture of the AVA, its gain at higher frequencies is improved. Therefore, the gain variation tends to be smooth straight line in the whole operating frequency bands. The proposed antenna structure including feeding line measures 12.9 x 6.8 x 0.254 mm 3 . The simulated results show that the gain is about 9 dB in the operating frequency band of 24.75-27.5 GHz, which makes it suitable for millimeter-wave 5G communications.