Two different poly(benzylmalate) biopolymers, a hydrophobic non-PEGylated (PMLABe 73 ) and an amphiphilic PEGylated derivative (PEG 42 -b-PMLABe 73 ), have been used to encapsulate a phthalocyanine chosen for its substitution pattern that is highly suitable for photodynamic therapy. Different phthalocyanine/(co)polymers ratios have been used for the nanoprecipitation. A set of six nanoparticles has been obtained. If the amphiphilic PEGylated copolymer proved to be slightly more efficient for the encapsulation and to lower the aggregation of the phthalocyanine inside the nanoparticles, it is, however, the hydrophobic PMLABe 73 -based nanoparticles that exhibited the best photodynamic efficiency.