Enzyme-catalyzed polymerization in vitro has gained considerable attention in the last two decades as an efficient tool in the polymerization of various monomers, such as saccharides, esters, phenols, and aromatic anilines; however, the polymerization of vinyl monomers using enzymes has been more limited, perhaps due to the hydrophobicity of most common vinyl monomers. Enzyme-initiated miniemulsion polymerization is demonstrated herein as a way to polymerize hydrophobic vinyl monomers such as styrene. By application of enzyme-initiated radical polymerization in miniemulsion, stable poly(styrene) latexes are prepared with a particle size near 50 nm. A very small amount of enzyme and surfactant is required to facilitate the miniemulsion polymerization, whereas a relatively high polymerization rate and conversion are achieved.