This study investigated the effects of expertise-based training (XBT) supported with videos including expert teachers’ shared experiences in a real class environment on preservice science teachers’ science teaching self-efficacy, in addition to their perceptions on the effects of XBT. The participants were 32 preservice science teachers registered for Methods of Teaching Science I. The methodology of the study was concurrent triangulation mixed methods research design. The data were collected through the Science Teaching Efficacy Belief Instrument (STEBI), open-ended questionnaires following experts’ videos, observations, and interviews. During analysis, a paired t-test wasconducted for quantitative data, and open coding analysis was applied for qualitative data. The quantitative results showed that after the intervention, science teaching efficacy beliefs increased. Moreover, the qualitative data showed that preservice science teachers learned a great deal about the application of teaching methods.