Background The purpose of this study was to explore alignment between reform-based Turkish primary science curriculum and alternative assessment practices of a classroom teacher. Materials and methods Observational case study approach was utilized. A classroom teacher with 32-year experience and his 31 students participated in the study. The data were collected throughout an academic year via classroom observations, teacher interviews, instructional materials and a science teaching belief instrument. Results Analysis of the data indicated that the teacher’s use of traditional assessment activities was more dominant than alternative assessment activities although the latter was strongly emphasized by the curriculum. Moreover, implementation of alternative assessment activities was not in line with what the curriculum stated. Conclusions Decisions of policy makers, lack of instructional time, exclusion of the curriculum by the teacher, inadequate pedagogical content knowledge and insufficient teacher training on assessment were found to be the elements that might affect the alignment negatively. Possible actions that may support in getting high alignment were discussed.