Development of bio-nanoreinforcement is gaining momentum worldwide nowadays since it contributes much to the green materials era. This paper presents a proposal for reusing the agro waste to produce cellulose nanofibres in an ecofriendly way. The present work aims to isolate cellulose nanofibres (CNF) from pineapple leaf fibres (PALF) via green-cost effective route using lime juice for acid hydrolysis and ball milling for defibrillation. PALF is considered as a waste material after the cultivation of fruits. But PALF is rich in cellulose, fully biodegradable and renewable which makes it a perfect candidate for the extraction of CNF. The main objective of the present work is to avoid the use of hazardous acids and reduce the high energy consumption for the isolation of cellulose nanofibres. Nowadays the use of these green methods is relevant in order to prevent pollution in the environment. The extracted fibres have been characterised by FT-IR, XRD, FESEM, HRTEM, AFM, DLS and Thermal analysis. FT-IR results show the isolation of cellulose nanofibres by losing hemicellulose and lignin. In XRD, the increase in crystallinity (77%) is a clear indication of removal of lignin and hemicellulose present in amorphous region. The Thermal analysis reveals that the thermal stability increases for the isolated nanofibres. The maximum degradation temperature observed for isolated CNF is 344.49 °C. The surface morphological analysis (AFM, FESEM and HRTEM) showed that lime juice hydrolysis and ball milling have been a successful method for the isolation of cellulose nanofibres which can be used an effective reinforcement for preparation of polymer nanocomposites. The diameter of CNF from FESEM, HRTEM and DLS obtained was around 30-85 nm, 10-50 nm and 420 nm respectively. Present work points out the chances of recycling the agro waste (pineapple leaves) to extract cellulose nanofibres and thereby preserving nature in an environmentally benign way. Analysis of production cost reveals that the proposed green methodology is economic, able to produce CNF on a large scale and can be utilized in food industry, paper making, biomedicine and machinery tools.