Classroom assessment is an essential part of education. The study investigated teachers' perceptions of classroom assessment and their current classroom assessments practices in secondary science in Bangladesh. Specifically, the study sought to gain an understanding of to what extent teachers use different classroom assessment strategies to understand and to support both teaching and learning processes and how their perception is related with their classroom assessment practice. The study was mainly quantitative with some integration of qualitative approach. Data sources were secondary science teachers and their science classrooms. The study used a questionnaire to establish the teachers' perceptions of classroom assessment in science, a lesson observation protocol, and pre-lesson and post-lesson observation interview protocols as main sources of data collection. A total of thirty teachers (twenty male and ten female) were chosen randomly from six secondary schools in Dhaka city. The findings suggest that teachers perceive classroom assessment as summative assessment. What teachers said about their classroom assessment practice was not reflected during their teaching. Therefore, the teachers' perceptions of classroom assessment have no significant relation with their classroom assessment practices.