Children are vulnerable in earthquakes, but they are also essential to foster earthquake-resilient communities. It is critical to enhance the preparedness of children against earthquakes through effective education and training. Immersive virtual reality (IVR) and serious games (SGs) are innovative digital technologies that enable realistic and engaging training environments. However, little research has been made on the applications of IVR SGs for earthquake training targeting children. In order to fill this gap, this paper presents an IVR SG training system based on a problem-based gaming framework. Three instructional mechanisms within the training system, namely prior instruction, immediate feedback, and post-game assessment, were investigated to promote learning through effective reflection. A controlled experiment involving 125 secondary school students aged from 11 to 15 years old was undertaken, using leaflets as a traditional training approach for the control group and the IVR SG training system as the main intervention. Results revealed that the IVR SG training system with post-game assessment was the most effective way to train children, with greater knowledge acquisition and self-efficacy improvement observed. Possible improvements, such as increasing the time for reflection and differentiating the stimulation between positive and negative feedback, are suggested for further research.