Purpose: The demonstration meetings are the most common interprofessional education (IPE) method. However, the effectiveness of the demonstration meetings is still unknown. This study tries to explore the effectiveness of the interprofessional demonstration meeting. Methods: This was a descriptive correlational study. We attempted to develop the "scale for the effectiveness of interprofessional demonstration meetings" based on the four core competencies of IPEC. The average CVI value scored by experts was 0.93. Two factors were extracted by exploratory factor analysis (EFA), including Interprofessional observation (IPO) subscale and Interprofessional application (IPA) subscale, and their total explanation variation was 68.61%. Cronbach's α coefficient of the scale was 0.96. The results showed the effectiveness scale has good validity and reliability. Results: 184 participants joined this study from June to July 2020. The results showed that the preceptors' scores of most items were significantly higher than trainees (p < 0.05) except three items. However, there was no difference in the effectiveness scores of "professions," "colearning," "pre-course case summary," or "participation times." There was a significant difference in whether the personnel who read the case summary before the course could actively participate in the meeting (F value = 9.24, p = 0.004). Conclusions: The results show that the "scale for the effectiveness of interprofessional demonstration meetings" was validity and reliable instrument, and the preceptors' self-assessment effectiveness is significantly higher than trainees. Preceptors should take advantage of their own experience to guide trainees on observational learning and to have better teaching outcomes.