A novel chloroindium(III) phthalocyanine network polymer (4) was prepared and characterized by energy dispersive X-ray spectrometry, proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA) and absorption and emission spectroscopies. The non-linear optical (NLO) profile of the prepared phthalocyanine (Pc) network polymer, derived from a nanosecond open-aperture Z-scan technique at 532 nm, shows a clear reverse saturable absorption and a high non-linear absorption coefficient ( α2) of 9.7 × 10−7 cm W−1. Optical limiting investigations indicated that the prepared Pc network polymer has a relatively low limiting threshold of 900 mJ cm−2. According to these results, the prepared Pc polymer is a promising material for many NLO applications.