The escalating environmental concerns associated with conventional plastics drive an urgent search for more sustainable food packaging solutions, with particular emphasis on biodegradable films derived from biopolymers. In this context, the valorization of agro-industrial waste, often rich in polysaccharides and proteins, represents a promising strategy. This study investigated the development and characterization of biodegradable films based on citrus pectin and isolated sunflower seed protein (PISG), both individually and in blends (Pectin/PISG 25:75). Buriti oil was evaluated as a potential plasticizing agent, partially (50%) and totally (100%) replacing glycerol. Films were produced via the casting method and characterized in terms of moisture content, water solubility, optical, barrier, mechanical, and thermogravimetric properties, as well as their biodegradability. The results demonstrated that the substitution of glycerol with buriti oil significantly altered the films' properties. A general trend of reduced moisture content and water solubility was observed with increasing oil content, particularly evident in protein-based films. Regarding optical properties, oil incorporation intensified the color in all formulations, with a more pronounced effect in protein matrices. The barrier properties were positively influenced by adding oil, showing a reduction in both water vapor and oxygen permeability. However, the complete replacement of glycerol led to a marked loss of flexibility and increased brittleness in the films, particularly for protein-based formulations. Thermogravimetric analysis indicated that buriti oil generally enhanced the thermal stability of the films. Biodegradability was modulated, with oil-containing films exhibiting a longer degradation time, suggesting improved durability without compromising their inherent biodegradability. In conclusion, buriti oil is a promising additive for enhancing the hydrophobicity and barrier properties of pectin and sunflower seed protein films. Nevertheless, optimizing its mechanical properties, potentially through its combination with other plasticizers or by improving incorporation techniques, is crucial for its successful application in sustainable food packaging systems.