Reviews concerning the enhancement of preschool children's social competencies reveal areas within which teacher approach, definitions of social competence and methods of study can be enhanced. In response, teachers and researchers co-developed and introduced a peer-based relational intervention to support children's communication, empathic response and non-homophilic choice of friendship/work mates. Within this design-based approach, a three-phase comparison was made in 14 English preschool classrooms. Results identified changes attributed to the intervention regarding: teacher behaviour (movement from giving directions to observation and support); child behaviour (enhanced reciprocal communication, empathic response to others and engagement in cognitively challenging activities) and an expansion of socially inclusive play/work mates. Not all teachers/classes responded to the relational approach in the same manner: those that engaged actively in the approach encouraged more social competence enhancements amongst children; those with lower engagement identified support/implementation problems and children showed less social competence advances.