Inclusive education refers to an educational approach in which all students can learn and participate in the mainstream school system. The successful implementation of inclusive practices is strongly determined by teachers' attitudes toward inclusive education and teacher training is one of several factors influencing these attitudes. Given the diversity of such programs, the present narrative review investigated the optimal design for pre-service inclusive teacher programs in terms of its duration and content delivery mode. For this, we considered and analyzed 31 studies, comprising 36 international interventions. Although most studies did not adequately report statistics to draw unequivocal conclusions, our results suggest an overall positive effect of training on pre-service teacher attitudes toward inclusive education. The effects of the duration and delivery mode of such programs are discussed from the perspective of successful training design in the light of social psychological theories and empirical findings, thus providing novel avenues for future research.