A comparative analysis of a compact planar Square patch Microstrip Multiband antenna on three different substrates is proposed. The proposed design has a C-shaped slot etched on the square radiating part and the antenna is energized using microstrip feed line. RT Duroid (ε _r= 2.2), Taconic (ε _r= 3.2) and FR4 (ε _r= 4.4) substrates are used for simulation analysis. The flow of current is modified by the C-shaped slot making the antenna to resonate at 3/4 and 6 bands for RT Duroid/Taconic and FR4 substrates respectively suitable for 5G sub GHz applications. The antenna has a compact dimension of 32 × 32 × 1.6 mm ³ and exhibits a return loss, S11 of less than -10dB for all the resonating frequencies for all three substrates. The analysis has been done by considering the S11 (Return loss <-10 dB), Directivity, Antenna Gain, VSWR and surface current distribution. Table II provides the comparison of parameters for different substrate material.