Synthetic plastics like polyolefins, acrylics which are widely used in consumer products are not biodegraded by microorganisms in the environment. The accumulation of plastics in the environment becomes a matter of great concern leading to long-term environment, economic and waste management problems. In order to overcome these problems, significant attention has been given on biodegradable polymers, and also, on the identification of microorganisms with degrading potential upon polymeric materials. Therefore, recycling and biodegradation of these polymers is an important issue for environmental protection. The present work evaluates the effect of Maleic anhydride (MA) and Methylmethacrylate (MMA) modified cellulose micro and nano fibres (MACF and MMCF respectively) on the biodegradation behaviour of Polymethylmethacrylate (PMMA)/cellulose composites. MA and MMA modified cellulose reinforced PMMA composite granules were prepared by in-situ suspension polymerization technique. PMMA/cellulose composite films were prepared by solution casting method and the biodegradation behaviour of the films was studied by soil burial method in two types of soils (Soil A and Soil B). The biodegraded films were characterized by weight loss study, viscosity average molecular weights, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (NMR). The isolation and identification of the fungus, which degraded these composites, were done for the first time along with the biodegradation study with the isolated pure culture. © 2013 Elsevier Ltd. All rights reserved.