Almond blanched skins (BS) and blanch water (BW) are underutilized agro-industrial by-products, despite their richness in polyphenols and other bioactive compounds. This study investigates the reuse of BW as an extraction solvent to recover polyphenols from BS, avoiding the need for additional water or organic solvents. BW showed a total polyphenol content (TPC) of 475.2 ± 10.7 μg GAE/mL and a Total Antioxidant Capacity (TAC) of 840.4 ± 41.8 μM TE. Thermal extraction at 115 ◦C and 1.7 atm for 1 h (1:10 BS/BW w/v) produced an enriched blanch water (EBW) with a TPC of 809.2 ± 12.1 μg GAE/mL and a TAC of 2188.8 ± 3.6 μM TE. Subsequent microfiltration and nanofiltration further concentrated the bioactive fraction, with the nanofiltration retentate exhibiting a 2.8-fold increase in TPC and a 2.1-fold increase in TAC compared to the EBW feed. Spray-drying generated a fine, homogeneous, and storage-stable powder without loss of antioxidant capacity. UHPLC-QqTOF-MS/MS analysis identified catechins and their derivatives, procyanidins, and flavanol glycosides as the main polyphenols contributing to the strong antioxidant capacity of the powder. Overall, this workflow provides a scalable and water-saving strategy to convert almond-processing residues into high-value functional ingredients for food, cosmetic, and pharmaceutical applications.