This paper deals with the design and parametric study of a miniaturized elliptical slot microstrip antenna with defect ground structure (DGS). The antenna is fabricated on a FR4 substrate with dimensions of 40 × 40 × 1.6 mm³. The systematic design of the antenna involves incorporating slots into the radiating patch and altering the ground plane structure. The parameters considered include slot ratio effect and the effect of ground defects on the resonant frequency, return loss, bandwidth, and gain. The original design of the antenna is characterized by dual bands with narrow bandwidth. When successive changes are made to the slots, the antenna becomes a multiband antenna. The inclusion of DGS greatly improves the performance of the antenna with an ultrawide bandwidth of 6.33 GHz, good return loss of −37.45 dB, and gain 4.9 dBi.