The first nanoprecipitation study of hydrophobic branched vinyl polymers is presented with control across a wide range of particle diameters (approximately 60–800 nm) from control of degree of polymerisation and precipitation parameters. In contrast to linear polymers of identical primary chain length, the formation of stable nanoparticles in aqueous media appears to be architecture driven with a contribution from oligomeric chain-ends with measureable water-solubility. The aqueous nanoparticles dispersions are robust and stable to dilution, solvent addition, sonication and temperature. The addition of small amounts of NaCl led to a destabilisation indicating charge stabilisation is also a major contributor to stability