Pumpkins are popular and adaptable Cucurbitaceous vegetables that have drawn a lot of attention due to their many phytochemical and health benefits. However, little research has been done on the by-products produced by the pumpkin-processing industry. Perhaps because of their functional components, these by-products, which include peels, seeds, seed oil, and seed cakes, have a wide variety of inventive applications in several industrial sectors. This comprehensive chapter seeks to give a thorough summary of the phytochemical and nutritional components included in pumpkin by-products, as well as information on how they are extracted, their health advantages, and the variety of food and industrial uses they have. The food, feed, pharmaceutical, cosmetic, and biofuel industries may find use for pumpkin peel, seeds, seed oil, and seed cakes because they include bioactive and functional components that work as potent antioxidants and antibacterial agents. Since pumpkins have good phytochemistry and can have favorable effects on food, health, and the economy, no part of the pumpkin should be regarded as waste during processing. For food scientists looking to reconsider the possibility of these by-products as functional ingredients, this research can provide insightful information. By increasing the market presence of sustainable and useful products that reduce food waste and promote health, reusing these by-products would help integrate a circular economy approach. Advanced analytical and green processing technologies are required to be implemented to isolate and purify the bioactive components from these pumpkin-processing by-products, and then their applicability and usefulness in different food and living systems could be investigated through different in vitro and in vivo assays.