The by-products of Galega kale, composed mainly of stems and leaves, represent an interesting source of bioactive compounds with various functionalities. The aim of this work was to develop and characterise functional pectin-based films using Galega kale powder as fillers, obtained from by-products of vegetable processing. The fresh by-products were blanched (100 ℃/ 30 s), dried (80 ℃/ 8 h) and milled, followed by their characterization in terms of total phenolic content and antioxidant activity. Pectin films were produced using the casting method, and characterized in terms of their bioactive, optical, mechanical and hygroscopic properties. Adding the by-products powder into the pectin matrix (0, 5, 10 and 20%) makes the films opaquer and with a more heterogeneous and yellowish colour. The incorporation of Galega kale powder at 20% significantly increased the films tensile stress at break (89%) and Young’s modulus (230%), compared to that of control film. However, water vapour permeability decreased around 45%. The same film showed higher total phenolic content (0.96 ± 0.08 mg GAE.g−1 dw), higher antioxidant potential with DPPH (2.94 ± 0.61 µmol TE.g−1 dw), ABTS (2.12 ± 0.24 µmol TE.g−1 dw) and FRAP methods (6.04 ± 1.47 µmol TE.g−1 dw). Thus, Galega kale by-products could be valued with the production of low-cost and environmentally friendly biodegradable films, with potential to be used in active packages with antioxidant activity.