The choice of suitable materials for constructing municipal solid waste landfills has been a significant research focus, as researchers aim to explore various waste materials for potential use in these projects. Conventionally, sand-bentonite mixtures are commonly used in suitable proportions, along with various other geotextile materials available commercially. Many studies are also available on waste materials like fly ash mixed with bentonite in different proportions, etc. However, a combination of fly ash and bentonite with natural fibre is very limited in these areas of application. Hence, this study was carried out to investigate the strength characteristics of fly ash-bentonite-coir fibre mixes at suitable proportions. The bentonite (B) and coir fibre (CF) proportions used in the present study are 5%, 10%, 15%, and 20%, and 0.5%, 1%, 1.5%, and 2% with fly ash (FA), respectively. The unconfined compressive strength (UCS) revealed that the bentonite (B) mixed with FA resulted in an improvement in strength. Further, it is observed that a 1% CF and 15% B mixture resulted in an improvement of UCS as compared to FA treated with 15% B alone.