A strategy to modify the latex particle morphology by means of block copolymers produced in-situ by controlled radical polymerization ( CRP) is presented. The strategy consisted in adding during the formation of the seed a small amount of a CRP agent, so that at the end of the seed formation some of the polymer chains were capped with the CRP agent. Polymerization of the second stage monomer in the presence of additional initiator led to the formation of some block copolymer chains that help to compatibilize the two polymers. This strategy substantially affected particle morphology. The effect of the proposed strategy on particle morphology was analyzed in terms of the underlying thermodynamic and kinetic factors.