Research has consistently stressed that regular school teachers are important in determining the success of implementing inclusive education. It was also found that teachers' attitudes, their knowledge about special educational needs (SEN) and teaching strategies are prerequisites for implementing inclusive education successfully. This study examines the effects of an in-service teacher training programme on regular primary school teachers' attitudes and knowledge about SEN and about teaching strategies. A pre- and post-test control group design study was set up (N[subscript experimental group] = 33, N[subscript control group] = 34), comprising 11 public primary schools. The training programme consisted of 32 hours face-to-face training sessions, covering topics about attitudes and knowledge about SEN and about teaching strategies. In order to establish the effects of the training programme, attitudes and knowledge were measured at two moments: before and after the training programme was performed. The outcomes of ANCOVA revealed significant positive effects of the training programme on most dependent variables (attitudes, knowledge about SEN and about teaching strategies) with medium to large effect sizes. Implications for future research and practice are discussed.