Case studies have been found to increase students' critical thinking and problem-solving skills, higher-order thinking skills, conceptual change, and their motivation to learn. Despite the popularity of the case study approach within engineering, the empirical research on the effectiveness of case studies is limited and the research that does exist has primarily focused on student perceptions of their learning rather than actual learning outcomes. This paper describes an investigation of the impact of case-based instruction on undergraduate mechanical engineering students' conceptual understanding and their attitudes towards the use of case studies. Seventy-three students from two sections of the same mechanical engineering course participated in this study. The two sections were both taught using traditional lecture and case teaching methods. Participants completed pre-tests, post-tests, and a survey to assess their conceptual understanding and engagement. Results suggested that the majority of participants felt the use of case studies was engaging and added a lot of realism to the class. There were no significant differences between traditional lecture and case teaching method on students' conceptual understanding. However, the use of case studies did no harm to students' understanding while making the content more relevant to students. Case-based instruction can be beneficial for students in terms of actively engaging them and allowing them to see the application and/or relevance of engineering to the real world.