Padang City is one of the cities in West Sumatra, Indonesia, with a high risk of earthquakes and tsunamis due to its location near the Eurasian and Indo-Australian Plates border. The SMAN 1 high school building is an educational facility in the city, built in 2010. The building was constructed from a steel–concrete composite structure, designed using the old Indonesian seismic code (SNI 1726:2002) and structural steel building code (SNI 1729:2002), so it should be evaluated using the current Indonesian building codes. In this study, structural assessment for earthquake and tsunami loads is conducted on the existing school building using the finite element program computer, ETABS. In contrast, the vulnerability assessment is carried out using fragility curves. The seismic fragility curve is determined from the maximum displacement of the building for each variation of earthquake acceleration using non-linear time history dynamic response analysis, which was scaled using the Incremental Dynamic Analysis (IDA) method and damage limit using Applied Technology Council (ATC-40) characterized by Hazus. Meanwhile, the tsunami fragility curve is established based on the maximum displacement under varying tsunami inundation depths. The results of the structural assessment indicate that the building cannot support the loads on its structural elements, and the inter-story drift does not meet the current Indonesian building codes. Meanwhile, the vulnerability assessment results show that the seismic fragility curve has a sequential probability of 100% for slight, moderate, and extensive damages, with an 86% probability of complete damage at peak ground acceleration (PGA) of 0.6 g. In addition, the tsunami fragility curve indicates a 100% probability of slight, 98% of moderate, 43% of extensive, and 0% of complete damages at a tsunami wave height of 5.00 m for Padang City, Indonesia.