Nanomaterials constructed by self-assembly of biomolecules are of particular interest as drug delivery carriers in biomedicine. However, supramolecular construction of nanoparticles by self-assembly of highly hydrophilic biomolecules such as hyaluronic acid still remains a formidable challenge due to their water solubility. Herein, we propose a strategy to fabricate stable nanoparticles by self-assembly of hyaluronic acid without the need of modification by hydrophobic groups. This strategy involves the electrostatic assembly of hyaluronic acid and naturally produced epsilon-polylysine and the in situ crosslinking by disulfide bonds. The resulting nanoparticles have the advantages of resistance to dilution, tunable size and surface charge, and efficient encapsulation of Chlorin e6 (Ce6), a photosensitizer for photodynamic therapy (PDT). In addition, the release of Ce6 from the nanoparticles is synergistically responsive to variations of pH and GSH levels. In vitro experiments reveal that the Ce6-loaded nanoparticles exhibit enhanced cellular uptake, improved phototoxicity, and unaltered biocompatibility as compared to unencapsulated Ce6, demonstrating that the nanoparticles constructed by self-assembly of hyaluronic acid are efficient and biocompatible drug delivery carriers for PDT agents.