In this work, three different extraction procedures were performed in Gleditsia triacanthos seeds in order to obtain extracts that were characterized in terms of the yield of extraction, total phenolic content and antioxidant properties. The extracts have been shown to contain considerable amounts of phenolic compounds (between 4.93 and 12.34 mg galicacid g extract ??? 1) and antioxidant activity between 18.77 and 71.59%. Different concentrations of one of the extracts (extract presenting simultaneously the best values of total phenolic content, radical scavenging activity and the concentration of the compounds that caused a 50% inhibition of the radical scavenging activity) were incorporated into G. triacanthos galactomannan solutions and films were cast from these. A 2 2 full factorial design was done to evaluate the effect of the galactomannan and extract concentrations in film properties. Galactomannan concentrations ranging from 0.5 to 1.5% and extract concentrations ranging from 0 to 1.0%, were used and the evaluated film properties as: water vapour permeability, colour, total phenolic compounds content and antioxidant activity. This work has shown that G. triacanthos can be used not only as a source of galactomannan films suitable to incorporate antioxidant compounds for further application in the food industry but also as a source of the active compounds to be incorporated. ; Funda????o para a Ci??ncia e Tecnologia (FCT) - SFRH/BD/ 23897/2005; SFRH/BD/32566/2006 ; Coordena????o de Aperfei??oamento de Pessoal de N??vel Superior (CAPES, Brazil).