This study investigated the physical, chemical, and phenolic properties of watermelon peel powder (WPP), watermelon rind powder (WRP), and watermelon seed powder (WSP) derived from watermelon (Crimson sweet) by-products (WBP). As these by-products are typically discarded as waste, the aim was to enhance their added value and explore their potential as sustainable functional food additives. WSP has the largest particle size among the samples. The highest water holding capacity was observed in WRP (8.89%) and oil holding capacity in WPP (4.09%), while WSP had the lowest (6.69% and 2.06%). WRP exhibited better rehydration and solubility, whereas WSP had lower values. WSP contained higher protein and lipid levels (29.46% and 43.0%), while WPP and WRP had greater dietary fiber (78.55% and 48.66%). In terms of mineral matters, Mg and K were substantially greater in WBP than Fe and Na
furthermore, WRP had more K and Mg than the rest. The total phenolic content was determined to be 2855, 3330, and 4196.5 mg GAE/100 g for the WRP, WSP and WPP, respectively. The antioxidant activity as measured by IC50 values, varied between 44.42 (WPP) and 121.29 mg/mL (WRP). A total of 47 phenolic acids were characterised, with genistein being the most abundant compound identified at 10147.1 µg/kg throughout all three powders. In conclusion, these findings highlight the potential of WBP as a sustainable ingredient for the food industry, offering both high nutritional value and functional properties. By valorizing watermelon by-products, this study contributes to waste reduction and supports the development of eco-friendly, nutrient-rich food formulations.