The aim of this study is to examine how middle school mathematics teachers diagnose and attempt to eliminate students' misconceptions in algebra. The study employed a case study method and embedded single-case design. The research was conducted with three mathematics teachers working in different state schools and having different professional experiences, as well as ten students from the eighth-grade classes of the same schools. The data collection instruments used in the study included the Diagnostic Test developed by researchers to identify students with misconceptions, the Assessment Framework prepared for the evaluation of teacher performances in diagnosing and eliminating student misconceptions, and Semi-Structured Interviews conducted between students and teachers, which were recorded and made available in audio/video format. The study revealed that teachers generally resorted to conventional methods in the process of diagnosing and eliminating students' misconceptions. In most cases, teachers superficially addressed students' errors and did not fully focus on students' thinking. Regarding the processes aimed at eliminating student misconceptions, teachers preferred to directly inform students that their answers were incorrect, rather than facilitating students in recognizing their own mistakes. The findings highlight the need to increase teachers' awareness and student knowledge regarding misconceptions in algebra.