The influence of polyoxymethylene (POM) additives on micro- and macrorheological proper-ties of polypropylene-copolyamide (PP/CPA) mixture melts with the PP/CPA ratios of 40/60 and 20/80 wt% was investigated. We have shown that the microrheological processes such as deformation of dispersed polymer droplets and formation of liquid polymer streams, coalescence of these streams along the longitudinal direction, migration, and fracture of the liquid streams into droplets can be controlled by addition of a third component that may interact with CPA in a specific manner. The ternary mixture melt viscosity was greater than that of the binary mixture melt viscosity. The degree of viscosity increase depended upon the composition of the binary mixture, the value of shear stress, and POM content. This dependence may be explained by formation of hydrogen bonds between POM and CPA macromolecules. The addition of POM improved the specific PP fiber formation in the matrix of CPA. The latter is valid even for a composition (PP/CPA ratio is 40/60) close to phase inversion. POM migration toward the walls of the forming die occurred in the flow of the ternary polymer mixture melts. For the purpose of realizing the specific fiber formation during the processing of the above mentioned mixtures we recommend an addition of 5% to 10% of POM.