Transparent adhesive polymer electrolytes, to be used for fabrication of electrochromic glass via a lamination process, were developed from gelatin blended with ethylene‐acrylic acid (EAA) copolymer ionomer resin. The gelatin‐based electrolyte films were prepared by mixing the polymer with glycerol, LiClO4, formaldehyde, and EAA in a microcompounder. The concentration effect of EAA (i.e., 2.5, 5, 10, and 20 wt% with respect to the gelatin) on thermomechanical, optical, and electrochemical properties of the prepared films were then studied. Results from atomic force micrographs revealed that surface roughness of the neat gelatin film significantly decreased after blending with 20 wt% EAA. This corresponds to the highest ionic conductivity value (4.46 × 10−6 S/cm) of gelatin‐based electrolyte in this study. Percentage light transmittance was also maintained above 80%, provided that the concentration of ionomer was kept below 20%. Finally, performance of the electrochromic device with a configuration of ITO/WO3/gelatin/NiO/ITO was demonstrated. Coloration efficiency and response time of 60.38 cm2/C and 10 s/50 s (coloring/bleaching) were achieved, respectively.