This paper presents the design and simulation aspects of tri-band stacked patch antenna for GPS and IRNSS applications. The antenna has two microstrip circular patch layers, which has different diameter to achieve the tri-bands frequency characteristics. The conducting body of antenna has two dominant resonant modes from patch 1 and patch 2 for L5 and L1 applications and one higher-order resonant mode for S-band application. The subtract is used Rogers RO4003C for antenna with dielectric constant 3.55 and loss tangent 0.0027. Coaxial probe feed location is selected such a way to excite two dominant modes and one higher-order mode. The ground segment stations use tri-band, i.e. L5-band from 1164.45 to 1188.45 MHz and S-band from 2483.50 to 2500.00 MHz for IRNSS application and L1-band from 1563.42 to 1587.42 MHz for GPS application. The proposed tri-band patch antenna is …