•Co-pyrolysis of biomass with plastics and coal, for the production of bio-oils is reviewed.•The progress of catalytic co-pyrolysis on upgrading of biomass-derived bio-oils is introduced.•The reaction mechanism between biomass and plastic in catalytic co-pyrolysis is described.•The functions of various acidic catalysts towards enhancement of bio-oil are addressed. Co-pyrolysis of biomass with abundantly available materials could be an economical method for production of bio-fuels. However, elimination of oxygenated compounds poses a considerable challenge. Catalytic co-pyrolysis is another potential technique for upgrading bio-oils for application as liquid fuels in standard engines. This technique promotes the production of high-quality bio-oil through acid catalyzed reduction of oxygenated compounds and mutagenic polyaromatic hydrocarbons. This work aims to review and summarize research progress on co-pyrolysis and catalytic co-pyrolysis, as well as their benefits on enhancement of bio-oils derived from biomass. This review focuses on the potential of plastic wastes and coal materials as co-feed in co-pyrolysis to produce valuable liquid fuel. This paper also proposes future directions for using this technique to obtain high yields of bio-oils.