A novel pattern reconfigurable antenna is proposed to achieve two different radiation patterns by controlling the bias voltage of switches. Initially, the proposed antenna operates as a top-loaded monopole antenna fed by a co-planar waveguide (CPW). When the slot from the CPW is disturbed by switching on PIN diodes, it operates as a slot antenna. Therefore, when the switch turns on, the maximum radiation intensity occurs at the normal to the aperture surface defined as the boresight direction, which is similar to a slot antenna. When the switch turns off, the maximum radiation intensity occurs at right angles to the boresight direction, which is similar to a monopole antenna. The pattern reconfigurable capability is successfully demonstrated at 2.3 GHz by full-wave simulation and measurement.