A 3-D cube antenna with application in wireless sensor network is presented in this letter. Employing microstrip-fed 3-D folded slot antenna topology, a horizontally polarized omnidirectional radiation pattern in azimuth plane was obtained. The structure that is compatible with 3-D printing was fabricated from RO3003 substrate and Objet VeroGray material. The interior of the cubic structure can be used to place electronic circuits of transceiver and sensor. Measurement results verify simulation, and a maximum gain of 1.95 dBi in the azimuth plane and bandwidth of 14% at the center frequency of 2.495 GHz were achieved. The cubic antenna has an edge length of 33 mm and covers the ISM 2.45-GHz frequency band, which has vast application in wireless sensor networks and telecommunication devices.