Nano-crystalline c-axis orientated indium nitride (InN) thin films were prepared on amorphous polycarbonate, polyimide and glass substrates by modified activated reactive evaporation (MARE) method without any intentional heating of the substrate. The films show strong visible photoluminescence (PL) peak at ~ 1.95 eV indicating the band edge transition which is in good agreement with the optical absorption. The shift in the band gap from reported value is mainly due to Burstein-Moss shift and presence of residual oxygen. InN film grown on inexpensive flexible substrates at room temperature opens opportunity for large scale device applications like solar cells and displays. © 2009 American Institute of Physics.