Multiphase flow industrial applications require reduced frictional pressure drop (drag) and lower operating costs. Drag reducing polymers (DRPs), which do not require additional infrastructure, meet this requirement. Therefore, this study investigated the effects of water-soluble polar ZETAG (R) 8165 and nonpolar oil-soluble polyisobutylene (PIB) DRPs on pressure gradient and percentage drag reduction using two-phase air-water and air-oil flows, and three-phase air-oil-water flow. The conduit comprised a 22.5 mm I.D. and 2.48 m long horizontal pipe. The fluid flow pattern and DRP shear stability were also studied. The functional mechanism of DRP, not adequately addressed in the literature, was especially revisited. This work suggests that the resultant interaction between the DRP state and the external environment dictates its ability for dampening turbulent eddies, streamlining the velocity field, and eventually increasing the thickness of the laminar sublayer. The DRP state includes its chemical structure and hydrodynamic size. On the other hand, the external environment comprises fluid flow pattern, polarity, phase morphology, and intensity of turbulence. Hence, the functional mode of a DRP is more involved than what the literature usually reports. ZETAG (R) 8165, having longer branches and ion-pairs around the backbone, showed less shear degradation than the fairly straight-chain PIB. The effects of these structural differences were also well reflected in their varying abilities to transpose flow pattern, and reduce drag and pressure gradient. For a given DRP, the air flow rate promoted or demoted the DRP performance, depending on the experimental design.