The present talk focuses mainly on the third order nonlinear optical (NLO) properties of organic phthalocyanine molecules in its thin film form. Phthalocyanines (Pc) are well known class of organic nonlinear optical molecules. The presence of highly delocalized π electrons in the macrocycle contributes to enhanced NLO characteristics of Pc molecules. Most of the previous studies carried out with Pc material in solution forms established these facts well. For practical applications of the material, study should be carried out in its solid state form. Peripherally substituted (tert-butyl) metal free and its metal (Cu and Zn) Pc materials were analyzed for this purpose in the thin film form. Third order NLO properties of TTBPc and its metal derivatives are studied using single beam Z-scan technique. Further, effects of 8MeV electron beam irradiation on NLO parameters of annealed Pc films are carried out. Impact of phase transition (α → β) on third and higher order NLO parameters of Pc thin films are also performed using fs Z-scan.