In this paper a high gain circular polarized microstrip patch antenna array for X-band CubeSat applications is presented. The array consists of 36 elements arranged in a square lattice of 6x6 presenting circular polarization with a -3dB axial ratio bandwidth of 3.8% at 10. 4GHz. The antenna array is printed on FR4 substrate to reduce the overall cost of the CubeSat while achieving a -10dB impedance bandwidth of 21%. Finally, the array is mounted on the top face of a 1U CubeSat providing a high gain of 20.1dB at 10. 4GHz with a -3dB gain bandwidth of 38.4%.