A printed microstrip-line-fed slot antenna with a pair of parasitic patches for bandwidth enhancement is proposed in this paper. By using the parasitic patches along the microstrip feed line, an additional resonance is excited and a good performance of bandwidth enhancement can be obtained. The proposed antenna is designed and manufactured successfully. The measurement shows a good agreement with the simulation. From the measured results, the enhanced impedance bandwidth, defined by voltage standing wave ratio (VSWR) less than 2, is about 136% ranging from 2.1 to 11.1 GHz. In addition, stable and nearly omnidirectional far-field radiation patterns are observed over the entire operating band.Index Terms-Bandwidth enhancement, microstrip-line-fed antenna, printed slot antenna, parasitic patch.