The possibility of using low concentrations of dialdehyde alginate (ADA) to crosslink and stabilize gelatin films was investigated. The films were prepared from gelatin solutions at different concentrations (5, 10 and 15 wt.%) containing different amounts of oxidized alginate (0, 1 and 3 wt.% with respect to the weight of gelatin). The extent of crosslinking increases as a function of ADA concentration, up to about 23%. The presence of oxidized alginate provokes a significant reduction in the degree of swelling and of gelatin release in phosphate-buffered saline solution, enhancing the effect of gelatin concentration. Furthermore, the values of the Young’s modulus, E, and of the stress at break, σb, increase with increasing ADA concentration. The observed small, but appreciable, increase in thermal stability found by differential scanning calorimetric investigation is supported by X-ray diffraction results.