We present a stabilization method of conjugated polymer nanoparticles (CPNs) through the creation of an inorganic shell on their surfaces, leading to a markedly improved preservation of the photophysical properties of the resulting nanohybrids in harsh radical environments as well as enhanced generation of reactive oxygen species (ROSs). The CPNs could be stabilized by partial photocrosslinking of an acetylenic alcohol, and maintained their morphological and photophysical properties in the reaction media used for the reduction of a silver precursor on their surfaces. The resulting nanohybrids, comprising a CPN core and a silver shell, displayed structural and photophysical stability in the harsh radical environments produced by the Fenton's reaction, demonstrating that the metal shell successfully shielded the polymer core from radical attack. In contrast to the pristine CPNs, the present nanohybridization significantly improved the photocatalytic activity, resulting in a more effective generation of ROSs. The nanohybridization described in this paper provides a practical solution for the long-standing problem affecting the applications of CPNs, the detrimental effect of ROS on the photophysical characteristics of conjugated polymers.