Fruit processing generates large amounts of by-products such as pomaces, which are rich in dietary fiber and bioactive compounds but remain underutilized. Their techno-functional properties, which determine their performance in food matrices, have rarely been characterized in pomaces used in their as-received industrial form, limiting their valorization. This study evaluated the physicochemical and techno-functional properties of apple, orange, and grape wine pomace flours obtained directly from industrial processing and assessed the effect of particle size reduction through milling (1, 0.5, and 0.25 mm mesh sizes). The pomace type had a stronger influence on techno-functional properties than the degree of milling, mainly due to compositional differences among raw materials. Apple pomace flour exhibited the highest hygroscopicity (24.2%), solubility (61.6%), bulk density, and the best flowability (Carr’s index 7.6%), suggesting suitability for dry mixes and instant formulations. Orange pomace flour showed high water retention capacity (5.0 g/g), swelling capacity, and low least gelation concentration (13.9%), indicating strong hydration and structuring potential. In contrast, grape wine pomace flour presented the highest content of insoluble fiber (lignin 42.7 g/100g) and water retention capacity (up to 6 g/g) but poor flowability and low solubility (11.6%), reflecting a predominantly structural behavior in food matrices. Increasing the degree of milling generally reduced particle size and flowability and, in some cases, increased hygroscopicity, which may influence powder stability during storage. These results provide relevant information for selecting suitable applications of fruit pomace flours and support the valorization of agroindustrial by-products as sustainable food ingredients.