Background/purpose: Computational Thinking is a content that has been integrated into primary education curricula in several countries. Its proper integration into education is not limited to its inclusion in the educational curricula, and teachers and pre-service teachers must develop the necessary knowledge to integrate it into their practices in an appropriate way. This article aims to evaluate the scientific knowledge of pre-service primary school teachers on Computational Thinking during a training program of a primary school context, through the analysis of their Levels of Knowledge and Performance on Computational Thinking across three moments (Pre-Intervention, Post-Intervention I, and Post-Intervention II) of task implementation of a 9- month training program. Materials/methods: This is a mixed-methods study, utilizing both quantitative and qualitative methods to analyze the scientific knowledge on Computational Thinking among 19 pre-service primary school teachers (mean age of 24.47 ± 9.576) enrolled in master's programs in Portugal during the academic year 2023/2024, who constitute the sample of this study. The scientific knowledge on Computational Thinking was evaluated through participants' Levels of Knowledge and Performance, using quantitative analysis across the three moments, complemented by a qualitative component that contextualized and deepened the interpretation of the results, enabling a more comprehensive understanding of their development throughout the training program. Results: The study results revealed statistically significant differences in the scientific knowledge on Computational Thinking of pre-service primary school teachers in terms of levels and performance on Computational Thinking, between Pre-Intervention, Post-Intervention I, and Post-Intervention II. In addition, they showed that the pre-service teachers improved their scientific knowledge throughout the implementation of the training program. Conclusion: The principal contribution of this study lies in outlining a procedure for assessing the scientific knowledge of pre-service primary school teachers regarding Computational Thinking within the context of initial teacher training.