The nonlinear absorption and optical limiting properties of two trimeric metallo-phthalocyanines namely, 2,4,6-tris[2-oxa-9,10.16,17,23,24-hexa(hexylthio) phthalocyaninato M(II)]-s-triazine (M=Zn for compound ZnPc and Cu for compound CuPc) doped polyvinyl chloride (PVC) thin film in the nanosecond regime were investigated by using the open-aperture Z-scan technique. The measurements were performed using 4 ns pulses generated from a frequency-doubled Nd:YAG laser at 532 nm wavelength. OL parameters of the ratio of the excited state to ground state absorption cross-sections kappa, the effective nonlinear absorption coefficient beta(eff), the linear absorption coefficient alpha(0) and the saturation density or energy density F-sat values were determined. The results show that MPc/PVC composite displays much larger nonlinear absorption coefficient and lower saturable fluence for optical limiting when compared to the same Pc molecules in solution. The results indicated that both compounds exhibited good OL performances. ZnPc shows slightly better OL parameters than that of CuPc. (C) 2011 Elsevier Ltd. All rights reserved.