A multiphase emulsion polymer for aqueous coating compositions containing little or no organic solvent includes at least one soft phase and at least one hard phase prepared by a multi-stage emulsion polymerization. The hard phase contains a hard phase polymer having a glass transition temperature in a range from 10 C to 100 C which is more than 50 C higher than that of the soft phase polymer. The hard phase is formed as a first stage polymer and the one soft phase is subsequently polymerized in the presence of the first stage polymer. The hard phase polymer includes at least one carboxylic acid monomer and at least one ethylenically unsaturated monomer. A method of making a multiphase emulsion polymer for aqueous coating compositions containing zero or low levels of organic solvent is disclosed. Such aqueous coating compositions may simultaneously have excellent block resistance, freeze thaw stability and low temperature coalescence characteristics.