The extensive use of composite products in numerous developing countries has significantly impacted human health, primarily due to the toxic synthetic adhesives employed in their production. This study aimed to develop a multifunctional adhesive using lignin and phytogenic protein (mustard oilcake) for producing composites from lignocellulosic materials without aldehydes. The adhesive formation process involved three steps. First, the wood was chipped at a thickness of 4 mm, and cooked in a digester at a temperature of 160 °C, using a 17% NaOH solution to extract lignin (black liquor). Next, the mustard oilcake was ground into a fine powder. The black liquor and powdered mustard oilcake were then mixed with a 35% citric acid solution. Finally, the resulting solid was mixed with a 35% citric acid solution and heated to 350 °C to form the adhesive. The physical, mechanical (shear strength), and chemical (viscosity, Fourier-transform infrared spectroscopy (FT-IR), Glass Transition Temperature (GTT), and Thermogravimetric Analysis (TGA)) properties of the adhesive were evaluated. The adhesive's average shear strength values were determined to be 4.70 and 4.67 MPa, respectively, according to ASTM D 905 and EN 205 standards. Compared to commercial urea-formaldehyde, the adhesive exhibited higher viscosity, longer gel time (58 seconds), and a higher glass transition temperature (170.6 ºC). Therefore, with further necessary studies, this adhesive can potentially be used by wood-based industries due to its lower cost and biodegradability.