Purpose: Children with special educational needs and disabilities (SEND) are often excluded from physical education (PE). Opportunities exist to enhance the competence of trainee teachers, thus preparing them for the demands of inclusive PE (IPE). In this study, we examined the effect of IPE training workshops on trainee teachers' self-efficacy for including SEND children within PE. Method: Data was collection from 366 trainee teachers across 44 workshops (63% females; 57% primary-school trainees; age, 23 ± 5 y, mean ± standard deviation; age range 18-53 y). A pre-post design was used to assess the effect of the workshop and possible moderating factors. Data were analyzed using mixed modelling. Results: IPE training had a large beneficial effect on trainees' self-efficacy (1.61, ±0.21; standardized effect size, 99% confidence limits). Mixed modelling revealed substantial differences in the mean outcome between workshops. The standard deviation (SD) representing this variation between workshops was moderate-sized (SD = 0.30, ±0.30). We also found that trainees with an above average sense of self-efficacy at baseline (mean +1SD) were likely to benefit more. Workshop size (0.35, ±0.42) and trainees' perception of workshop quality (0.39, ±0.19) were substantial moderators of changes in self-efficacy. Other moderators with possible substantial effects were trainee specialization and completion of a school-based placement. Conclusion: This study supports the viability of embedding IPE within teacher training. Attention should be paid to trainees' starting points prior to scheduling training. The size of workshops and quality of delivery should also be considered when developing IPE competencies within trainees.