Passion fruit (Passiflora edulis) is consumed worldwide, and its processing generates a substantial amount of waste, particularly from the seeds and peels. This study investigated the potential of valorizing passion fruit seeds by adding them to high-fiber snack bars. Seed-enriched snack bars were evaluated for their sensory qualities, antioxidant activities, and nutritional compositions. Seed addition markedly increased the dietary fiber content (from 4.17% to 5.66%), fat content (from 15.02% to 19.63%), and antioxidant activity (e.g., 83.38% vs. 82.47% DPPH inhibition at 50 ppm) compared to the control. This was mainly due to the presence of piceatannol, a potent bioactive molecule. The overall phenolic content decreased from 90.11 to 65.37 mg GAE/100 g, suggesting intricate matrix interactions. The control bars exhibited a higher overall acceptability score, whereas the seed bars remained within the acceptable sensory range and required only minor texture adjustments. Microbiological analyses confirmed that both formulations retained their safety for 7 days at +4 °C, with appropriate levels of yeast and total viable count and no mold growth. These results suggest that passion fruit seeds have the potential to be used as a sustainable functional food ingredient. Further research is warranted to improve the sensory qualities and shelf-life stability.