To provide a primer composition for polyolefins added in order to enable coating of a water borne acrylic coating onto the surface of a polyolefin material.

The primer composition for polyolefins is obtained by adding a rosin ester-based resin emulsion and/or a hydrocarbon-based resin emulsion as a viscosity-imparting agent to an emulsion obtained by dispersing a chlorinated polypropylene resin into a water system. A resin component in the adhesion-imparting agent is added in an amount of preferably 1-50 wt.%, more preferably 5-20 wt.% based on a resin component in the chlorinated polypropylene resin emulsion.