Given vortex-induced vibrations of bridges caused by high wind attack angles in mountainous canyons, this study investigated the vortex-induced dynamic characteristics of a Π-shaped steel-concrete composite beam cable-stayed bridge in a mountainous canyon under high wind attack angles based on wind tunnel tests and examined aerodynamic measures for vortex suppression. Firstly, a finite element model of the bridge was established, and the dynamic characteristics of the bridge in both the completed and construction states were analyzed. Subsequently, a 1∶50 scale detailed segment model was designed based on similarity theory to analyze the vortex-induced vibration performance of the original main beam under conventional wind attack angles of ±3° and 0°, as well as the high wind attack angle of ±5°. Then, the influence of a single aerodynamic measure such as L-shaped deflector plates, wind fairings, and lower stabilizing plates, as well as their combinations, on the vortex-induced vibration performance of the Π-shaped main beam was studied. Finally, the optimal aerodynamic measures and their performance improvements were proposed. The research reveals that the vortex-induced vibration performance of the Π-shaped beam cable-stayed bridge is poor, and significant vortex-induced vibrations occur at all five typical wind attack angles under low wind speeds. The single aerodynamic measure fails to control vortex-induced vibrations of the Π-shaped main beam. The combination of the 1^# wind fairing + lower stabilizing plate exhibits excellent vortex suppression effects, reducing the corresponding vortex-induced response displacement by over 95%. The research results can provide valuable insights for similar real-world engineering projects.