This study investigated the relationship between mathematics teachers' perceived use of formative assessment strategies and their levels of metacognitive regulation. The study employed a descriptive cross-sectional survey design using a sample of 213 (male=138; female=42) mathematics secondary school teachers from 50 randomly selected secondary schools in Kenya. The Teacher Assessment for Learning Questionnaire (TAFL-Q) was used to measures the mathematics teachers' perceptions of formative assessment whereas the Metacognitive regulation Inventory for Teachers (MAIT) scale was used to measure mathematics teachers' levels of metacognitive regulation. The relationship between the two scales was modeled using structural equation modeling and path analysis in AMOS graphics software. The measurement model fitted the data well with acceptable fit indices. The results of the model show that teachers evaluating skills are positively predicted by learning intentions, success criteria, and peer assessment. Monitoring skills are positively predicted by classroom discussion and peer assessment. Planning skills, on the other hand, are positively predicted by feedback, peer assessment, and success criteria. This study contributes to the limited literature regarding the relationship between formative assessment and metacognition. Teachers' understanding of this relationship will help in modeling learning strategies and skills in the learners.