Tsunami vertical evacuation (TVE) buildings have the potential to save many human lives in countries exposed to near-field tsunamis. Up to now, TVE research has examined three main topics separately: shelter siting, building benchmarks, and decision-making by evacuees. This study aims to integrate these topics to develop more comprehensive TVE planning frameworks. To this, we examined a catastrophic tsunami evacuation scenario in Viña del Mar, Chile. First, we developed an agent-based model to estimate potential human fatalities in the case of a fully horizontal evacuation. Second, we designed an immersive VR experience, which we applied to a sample of 151 people in the city to collect their potential TVE decision-making, which allowed us to identify 11 buildings that could serve as TVE shelters. Lastly, we incorporated this new evacuation system into the former agent-based model to assess the potential impact of vertical evacuation. Our findings showed that while fatalities ranged from 50 to 72% of the population in the fully horizontal scenario, the inclusion of TVE buildings might decrease human losses by 6.5–13.7%. Complementary questionnaires administered to participants highlighted their lack of previous experience in real-world evacuations (only 45.69% had previously experienced a tsunami-related evacuation process), as well as their knowledge about how to proceed in the case of a future emergency (62.91% declared that they knew where to go during an evacuation).