The ability to incorporate medium chain length poly(hydroxyalkanoate) (mcl-PHA) in the styrene miniemulsion polymerization process was investigated. As a result, novel poly(hydroxyalkanoate)-co-poly(stryrene) (PHA-co-PS) copolymers were synthesized in the form of stable organic–organic hybrid latexes. Evidence of chemical grafting of mcl-PHA and cross-linking of the PHA grafts was obtained using NMR, differential scanning calorimetry (DSC), gel extraction, and rheological analysis. A high degree of mcl-PHA grafting was achieved by maintaining proper miniemulsion polymerization conditions throughout the course of the polymerization. The incorporation of PHA grafts was a function of the level of PHA in the formulations as well as the reaction conditions, as evidenced by solvent extraction and rheological analysis. DSC showed shifts in the Tg of PS towards higher temperatures, indicating chemical interaction of PS-PHA.