This study reports mixed-methods research findings, which assesses the level of mathematics teachers’ pedagogical content knowledge (PCK) in selected secondary schools of Zanzibar. A Likert-scale questionnaire related to PCK self-assessment was administered to 69 teachers, 12 of whom were observed three times during lesson delivery in their respective mathematics classrooms. Both descriptive, inferential, and qualitative analyses were used. The study based on a questionnaire revealed that the level of mathematics teachers’ PCK was moderate. However, significant differences in the levels of PCK based on teacher’s education level and teaching experience were observed, while teachers’ specializations showed no significant differences in their PCK level. The findings based on observation indicate that the level of PCK in classroom practices is low. This indicates the teachers’ challenge in the implementation of PCK in classroom practices. There is, therefore, a need for more in-service training on raising teachers’ PCK levels, which will eventually lead to improved mathematics teaching and learning.