In recent years, many studies have focused on teachers' conceptions and their effects on instruction and learning. Accordingly, the present study aims to investigate the level of teacher's conceptions of assessment and comparison between gender and academic qualifications. It utilises a causal-comparative research design to investigate conceptions of assessment among 352 Iranian lower secondary level mathematics teachers using COA-III questionnaire. Results of the study find that math teachers exhibit moderate-level conceptions. Significant differences exist across the academic qualifications on Improvement and Irrelevance based on academic qualifications. Teachers with PhD qualifications have more in Improvement and Irrelevance than those with bachelor and master's degree holders. Only school accountability has significant difference between male and female teachers; male teachers exhibit more in school accountability than female teachers. Policy makers, teachers, researchers and school administrators should consider these findings in their practices to introduce and enhance alternative methods of assessment.