Development of natural fiber composites with thermoplastics and thermosets finds applications in various fields, from agriculture to automotive. It can reduce the dependency on petroleum resources which causes several environmental problems. Natural fibers are renewable and biodegradable that reduces carbon footprint to the environment. Coir fibers are natural fibers used in the development of composites offers comparable properties with other mineral fillers. This article reviews different methods of coir fiber modification include alkali treatment, silane treatment, hydrogen peroxide treatment, sodium hypochlorite treatment, sodium periodate treatment coupled with p‐aminophenol and urea, treatment with benzene diazonium salt and maleated coupling agent. It also reviews composites of coir fiber with thermoplastic, rubber and thermoset plastics. Hybrid composites based on coir fiber are also being discussed. Thermoplastic composites such as biodegradable (PLA, PBS) and petroleum‐based polymers (PE, PP) and thermoset polymers include polyurethane, epoxy and polyester based composites also reviewed. Degradation and biodegradation studies were reviewed in the case of biodegradable polymers. Hybrid fibers of coir with other natural and mineral fibers have recently been used in composite industry has also been reviewed. All these composites show better properties. It can be used in different applications in the field of automobile, building and construction, consumer products and furniture. POLYM. COMPOS., 37:3296–3309, 2016. © 2015 Society of Plastics Engineers