Pterocarya stenoptera bark extract (PSBE) was assessed for its chemical constituents, antioxidant activity, and antibacterial activity. The total phenolic content (TPC) in the PSBE was 272.92 ± 3.22 mg gallic acid equivalent (GAE)/g. Three phenolic compounds (quercetin-3-O-(2″-O-galloyl)-rhamnoside, quercetin, and juglone) were identified in the PSBE via ultraperformance liquid chromatography/mass spectroscopy (UPLC/MS) analysis. The PSBE possessed remarkable antioxidant activity in the DPPH and ABTS+ radicals scavenging system, with IC50 values of 96.25 ± 3.82 μg/mL and 158.26 ± 6.08 μg/mL, respectively. Moreover, the PSBE had high antibacterial activity, which was especially sensitive to Staphylococcus aureus. The antibacterial mechanism of the PSBE on the S. aureus was related to the deformation of the cell morphology and the destruction of the cell membrane structure, which was confirmed using a BacLight Viability Kit and scanning electron microscope (SEM) observations. These findings suggest that the strong antioxidant and antibacterial properties of the bark extract from P. stenoptera make the tree species suitable as a natural additive in the pharmaceutical, food, and cosmetic industries.