Oxidative stress plays a pivotal role in the onset and progression of chronic and metabolic diseases, including diabetes, obesity, and cancer, due to the excessive production of reactive oxygen species, which cause damage to essential biomolecules and impair critical cellular functions [1]. Antioxidants such as polyphenols can mitigate or delay this damage, driving growing interest in the use of polyphenol-rich extracts as natural functional food ingredients. Notably, polyphenols can be obtained from the massive amounts of undervalued plant biomass generated after crop harvesting [2]. Therefore, this study was caried out to valorize sweet pepper (Capsicum annuum L.) agricultural by-products as a source of bioactive polyphenols, in line with United Nations' 2030 Sustainable Development Goals. Hydroethanolic extracts were prepared from these plant by-products [2], and their phenolic profile was characterized using HPLC-DAD-ESI/MS. Additionally, the extracts' antioxidant, antidiabetic, anti-obesity, anti-inflammatory, and cytotoxic properties were assessed through in vitro cell-based and enzyme inhibition assays. Chromatographic analysis revealed a phenolic profile consisting mainly of phenolic acids, such as chlorogenic acid, and O-glycosylated flavones, specifically luteolin and apigenin. The extracts showed notable antioxidant and anti-diabetic properties, along with cytotoxicity against certain tumor cell lines. In conclusion, sweet pepper crop by-products are a promising source of bioactive compounds that can provide functional properties to foods and related products. Furthermore, this approach to resource circularity is crucial for promoting sustainable production and consumption patterns, contributing to a more eco-friendly and efficient use of agricultural resources. However, ensuring that the final products are free from pesticide residues and other contaminants will be essential for guaranteeing food safety.