We here report on a preparative, template-based method for oxidation-responsive, poly(propylene sulfide) cross-linked nanoparticles. In this study we demonstrate that preformed, narrow polydispersity, and end-functional polysulfides can be dispersed to yield stable emulsions, which can then be converted into stable nanoparticles through photochemically initiated cross-linking. The nanoparticle size is substantially templated on that of the precursor emulsions; the nanoparticles bulk is an elastomeric material with a homogeneous cross-linking density. The nanoparticles show a peculiar, two-stage behavior upon exposure to oxidants, which is likely composed of a first agglomeration phase followed by swelling.