A flying jet plasma torch (FJPT) was applied to treat raw polymers before the end use process. Specimens of the raw polymers (polypropylene, polystyrene, and two grades of polyethylene) were treated for a few minutes. The examined specimens were analyzed by using scanning electron microscopy, atomic force microscopy, and energy dispersive X-ray spectroscopy. The results indicated that FJPT effectively stimulated the topographical modifications and changed the chemical composition of the surface, which consequently affected the roughness of the surface. Machinability of the examined high-density polyethylene (HDPE) was investigated through measuring the melt mass flow rate index (MFI). The results showed that MFI increased around 30% after 5 min treatments. Longer treatment periods resulted in reductions of MFI attributed to thermal effects. Measured MFI for treated HDPE slightly decreased for 3 days after treatment. Hence, FJPT proved useful for treating polymer surface homogeneously and tailoring the surface chemistry for the required end use.