In the current study, three different commercially available copolymers are used as compatibilizer in carbon fiber (CF) reinforced high density polyethylene (PE) based composites. Polyethylene grafted maleic anhydride (PE-g-MA), a random terpolymer of ethylene, acrylic ester and maleic anhydride (LOT MA) and a random copolymer of ethylene and glycidyl methacrylate (LOT-GMA) are used as compatibilizers. The compatibilizers are used at three concentrations of 1.5, 3 and 6 wt%. The type and amount of compatibilizers on the tensile, impact, flexural, thermomechanical and morphological properties of composites are investigated. The use of coupling agents increases the mechanical properties of composites regardless of their type. The maximum increase in mechanical properties is observed at different concentrations of compatibilizer depending on the test type and compatibilizer type. The effectiveness of the compatibilizers is ranked as follow: LOT-MA > LOT-GMA > PE-g-MA in all mechanical tests. A correlation is observed between the effectiveness of compatibilizers and their polar group content. The higher polar group content causes the higher improvement in mechanical tests studied in this work. (C) 2016 Elsevier Ltd. All rights reserved.