Assessment is a powerful tool for raising the standards of teaching and learning of mathematics at the junior high school level. This study therefore explored the perceived influence of assessment on the teaching and learning of mathematics in junior high schools of OLA Circuit in Cape Coast Metropolitan area. The research design used for the study is a concurrent triangulation mixed method design. A simple random sampling technique was used to select four (4) public junior high schools out of eight (8) schools in the circuit. A multistage sampling procedure was employed to select the schools and participants for the study. A total of 134 participants comprising 15 teachers and 119 students participated in the study. The data for the study were mainly collected through questionnaires and interviews. Findings of the study revealed that class exercise, homework, and trial work were the most common mode of assessment used by teachers during mathematics instruction. Again, the study discovered that teachers faced some challenges in the implementation of classroom assessment. The study therefore makes certain recommendations likely to improve on the quality of assessment practices in mathematics classrooms in the focal schools.