This article addresses constructions and redefinitions of teacher professionalism by focusing on the discursive negotiations between the government and the teachers' union in Norway. Based on an examination of three white papers on teacher education from the past 15 years and policy documents put forth by the Union of Education Norway during the past decade, the authors argue that new constructions of teacher professionalism are produced both by the government and from within the teachers' union. However, there are differences between the government and the teachers' union concerning what the main aspects of teacher professionalism are. The government emphasises teacher accountability, research-based practice and specialisation. By contrast, the teachers' union highlights research-informed practice, responsibility for educational quality and professional ethics. There are three main areas of discursive struggle focused by the teachers' union: the resistance to accountability policies, the redefining of research-based practice and the lengthening of teacher education. The authors argue that the teachers' union is adopting an increasingly more active approach, thereby also challenging the idea that the teachers' union is less interested in developing and taking responsibility for the quality of school education. (Contains 1 table and 2 notes.)