Attention to the attitudes of primary teachers towards science is of fundamental importance to research on primary science education. The current article describes a large-scale research project that aims to overcome three main shortcomings in attitude research, i.e. lack of a strong theoretical concept of attitude, methodological flaws in attitude research, and ineffective interventions. The research project included: (a) the development of a new theoretical framework for teachers' attitudes towards (teaching) science, (b) a new validated survey instrument (the DAS) to measure the different underlying components of primary teachers' attitudes toward teaching science, and (c) an in-service professional development training course based on the previously developed theoretical framework. The framework of attitude consists of three dimensions: cognitive beliefs, affect, and perceived control, each consisting of several subcomponents. By means of the survey instrument we investigated the effects of the attitude focussed training course. The course aimed to improve attitude by creating awareness about teachers' own attitudes, stimulating their scientific attitudes and curiosity, and training inquiry and thinking skills. The course refrained from providing recipe-like example lessons, materials, or methods. Using a pre-post, experimental-control design we showed that the course significantly improved the affective and perceived control dimension of attitude. Teachers enjoyed teaching science more, showed increased self-efficacy, and felt less dependent on external factors. This project shows that genuine attitude improvements of primary teachers can be accomplished by attitude focussed professional development.