Myofibrilar protein-based films were developed from a film-forming solution based on fish mince. The thermal properties of these films were characterized by dynamical mechanical thermal analysis and by differential scanning calorimetry as a function of their water content. During a temperature increase, the films produced sudden changes in mechanical property and specific heat, which are classicaly associated with the glass-rubber transition for amorphous materials. The glass transition was about 20 degrees C broad. Increasing the film water content involved a non-linear decrease in glass transition temperature. The thermodynamic theory of the glass transition (i.e. the Couchman-Karasz equation) was inadequate to describe fully the plasticizing effect of water on the films.