In this paper, we describe the design and development of Flight Computer module of the nano-satellite of IIT Madras, named IITMSAT. The flight computer module uses a 32 bit ARM microcontroller from Freescale-KL46Z256VLL4 and handles the attitude control, beacon transmission and electrical power management functions. The data from the attitude sensors is used by the control algorithm to calculate the magnetic moment, and in turn the torque required to orient the satellite along the direction of the magnetic field of the Earth. Beacon signal is used to detect the visibility of the satellite by the ground station (GS) and to transmit some important health data of the satellite. Onboard power management is done by turning off the loads carefully to save power, whenever needed. Throughout the design phase, the cost was kept as low as possible, without compromising on the performance of the system. © 2015 IEEE.