The utilization of biodegradable materials for solid electrolyte membrane fabrication can solve disposal problem of waste created after its service life. Membranes fabricated as part of this work are eco-friendly in nature and also broaden the scope for using sustainable materials such as poly(vinyl alcohol) (PVA), chitosan (CS) and cellulose nanocrystals (CNCs) based technologies for future direct methanol fuel cell applications. Protonation of PVA-CS-CNC membranes resulted in improved proton conductivity, which is found to be in the range of 10(-4) S cm(-1). The different acid functionality and morphological dimensions of CNCs have an impact on water uptake (varying in the range: 68-253%), swelling behavior (varying in the range: 5-50%) and ion conductivity (varying in the range: 3.58x10(-5)-6.42x10(-4) S cm(-1)) of the prepared membranes which have been corroborated with CNC's aspect ratio using FESEM micrographs. Dynamic mechanical behavior analyses confirms that the PVA-CS-CNC membranes are found thermo-mechanically stable under dynamic load up to 120 degrees C which is well above the required fuel cell operating temperature. Although, crosslinking of the membranes have adversely converted crystalline phase of the membranes into amorphous, however the incorporation of CNCs, a crystalline nano-fillers in PVA matrix created tortuous path which suppressed the methanol permeability to 3.12x10(-8) cm(2) s(-1) that is significantly lower than that for the base PVA membrane methanol permeability 4.19x10(-7) em(2) s(-1).