Depression is a major psychiatric disorder in Brazil and worldwide. Vaccinium ashei (V. ashei) leaves are cultivation by-products with high bioactive compound levels. Here, a hydroalcoholic extract of V. ashei leaves (HEV) was associated with Eudragit® RS100-based nanoparticles (NPHEV) to evaluate the in vitro antioxidant and in vivo antidepressant-like effects. Interfacial deposition of the preformed polymer method was used for NPHEV production. The formulations were evaluated regarding physicochemical characteristics, antioxidant activity (DPPH radical scavenging and oxygen radical absorbance capacity), and antidepressant-like action (1–25 mg/kg, single intragastric administration) assessed in forced swimming and tail suspension tests in male Balb-C mice. The NPHEV presented sizes in the nanometric range (144–206 nm), positive zeta potential values (8–15 mV), polydispersity index below 0.2, and pH in the acid range. The phenolic compound content was near the theoretical values, although the rutin presented higher encapsulation efficiency (~95%) than the chlorogenic acid (~60%). The nanoencapsulation improved the HEV antioxidant effect and antidepressant-like action by reducing the immobility time in both behavioral tests. Hence, Eudragit® RS100 nanoparticles containing HEV were successfully obtained and are a promising alternative to manage depression.