One of the key messages of the contemporary approach to school development is that teacher participation is a necessary precondition for the successfulness of this process. Experience from the world, however, shows that broad and active participation of teachers in school development is neither easy to achieve nor to sustain in the long run. Similarly, the first experiences with school developmental planning in Serbia from the first half of this decade also pointed out to the differences with respect to readiness of teachers to take over this new role. The research that will be presented in this paper was conducted with the aim of discovering and determining the levels and ways in which different factors influence teacher involvement in developmental activities in school, whereby those activities are of cooperative and leadership character. The research was conducted on the sample of 385 teachers from 51 primary schools in Serbia. The findings indicate that teacher involvement in school development is a product of a complex combination and interaction of numerous personal and contextual factors, bearing in mind that harmony of personal and professional identity and meanings ascribed to changes in school is of primary importance. The final part of the paper provides recommendations for system and organizational level in order for teacher involvement in school development to become a widespread and sustainable practice.