In this study, which is aimed to investigate the balance principle of the secondary school science curriculum, a case study, one of the qualitative research methods, was employed. In the study, which was conducted by using case design, data analysis was performed by using teacher opinions, observation, and document analysis. The weighted kappa coefficient was calculated to ensure the validity of the observation results and to purify the results from the chance factor. It is not possible to make a definite definition of the balance principle and to state that a curriculum is in full balance. The concept of balance is always considered as an element that will be incomplete in one aspect. In this respect, it is concluded that student-centered curriculum understanding is in the forefront instead of subject-centered curriculum in the secondary school science curriculum, and it is compatible with student-society needs and width-depth element. In terms of learning areas, it was observed that the balance cognitive domain came to the forefront and the customized education dimension was lack. It is seen that the harmony between being open to innovations and traditional knowledge in the curriculum has been replaced by an instructional design based on the subject logic. In addition to general needs, suitable designs are applied successfully in situations requiring special needs. Similarly, it is seen that the curriculum has an adequate and balanced structure in terms of plans and measures to meet the needs of different students with academic development levels. For the implementation phase of the curriculum, it seen that different variables limit this dimension in terms of methods and techniques used. It has been observed that interdisciplinary harmony cannot be achieved with the connection established between past and present in relation to discipline and that students cannot demonstrate their expected transfer skills. It is thought that the lack of physical activity required by the students to transfer and internalize information is among the reasons for this situation. It was concluded that the opportunity to provide learning outside the classroom and the use of society as an educational laboratory was not included in the implementation of the curriculum.