Abstract Free radical and reverse atom transfer radical polymerization (ATRP) techniques has been applied in the synthesis of poly(octadecyl methacrylate) (POMA) to be evaluated as flow improver (FI) for waxy crude through rheological and morphological studies. Addition of POMA improves the flow ability of waxy crude as well as modulated the wax crystal morphology. The maximum reduction of apparent viscosity of waxy crude was observed at higher concentration of POMA that was synthesized via free radical polymerization and at lower concentration of POMA that was synthesized via reverse ATRP technique. The wax crystal morphological observation by polarized optical microscopy shows that POMA can strongly crystallize with wax molecules, and the size of wax crystals increases slightly and tends to form small wax crystal flocs, which greatly improves the rheological properties of the crude oil. Highlights Comb‐like polymer POMA synthesized via free radical and reverse ATRP methods. Effect of POMA on low‐temperature flow ability of crude oil was studied. POMA via free radical method efficiently lowers the crude oil gelation point. Crude oil viscosity significantly decreases with addition of synthesized POMA. Adding POMA via both methods significantly alters wax crystal size in crude oil.