Poor water and chemical resistance of pure biopolymeric films is a major barrier to their applications in the packaging industry. The present work involves an innovative and novel formulation of biopolymer nanocomposite utilizing a green fabrication process to produce a highly robust, chemically resistant system and printable, flexible polymeric film. This unique concept utilizes the electrostatic interaction between two biopolymeric materials (chitosan and sodium alginate) owing to their inherent functionality, which could be knowingly tuned just by changing the pH of the medium. The films are obtained from a hydrogel prepared by stepwise addition of the components as well as cross-linker in a designed manner. This is for the first time a biological alkaline extract containing carbon dots derived from banana corm (BCE CDs) is used as a cross-linker for biopolymers. In addition, mushroom was used to synthesize a nanofiber and used in the fabrication of nanocomposite film. The synthesis of lignocellulosic nanofibers from mushrooms that avoids the usage of any harmful chemicals in preparing the composite film is demonstrated. Fabricated films show tensile strengths up to ∼59 MPa after optimizing the composition. The film exhibited stability under both acidic and basic pH conditions even after being kept for 24 h. Additionally, it displayed resistance to a broad spectrum of organic solvents. In addition, the films can be used as a substrate for printing technologies, widening the scope of their use in packaging materials. Thus, the work demonstrates the fabrication of green, robust, edible, chemically resistant, and printable biobased nanocomposite flexible films.