This study aimed to determine and observe the topic-specific pedagogical content knowledge of university mathematics teachers before and during limit and continuity concept instruction, and compare the teachers’ perceptions of their teaching to what happened in their classrooms using the case study method. The study involved five university mathematics teachers who teach ‘Applied Mathematics I’ to pre-engineering students at Assosa University, Ethiopia. Classroom observation sessions and pre-lesson teacher interviews were used as data sources. The data were analyzed by identifying common themes in each of the knowledge components prior to and during the lesson, and then by comparing the two phases. The findings from the teacher cases provided detailed contextual information and revealed knowledge manifestations in their lesson design and actual teaching processes. The study’s findings revealed that teachers had a good understanding of topic-specific pedagogical content knowledge components prior to the lesson, but did not demonstrate most of these in their actual teaching of limit and continuity; their reported and enacted knowledge differed. According to this study, individual teachers varied in their implementation of what they had mentioned about various components of topic-specific pedagogical content knowledge. The study proposes that understanding teachers’ knowledge during the lesson design phase and actual teaching could help fill the gap as a means of professional development, and thereby, improve pre-engineering students’ mathematics learning.