This study investigated the effects of educators' mathematics pedagogical content knowledge on the mentoring of Grade 12 students using problem-based learning in two selected secondary schools in the Amajuba district in KwaZulu-Natal. The study collected qualitative data from four participating mathematics educators through the semi-structured interview questions that were presented to them. The data were analysed thematically according to the various sub-structures within Shulman’s theoretical framework. The investigation suggests that educators who are well versed in mathematics pedagogical content knowledge, are masters of Grade 12 mathematics content, which enables them to use various teaching methodologies to design and implement lessons to successfully overcome students' difficulties. To achieve this, educators need additional information, like the curriculum's scope, educational objectives, and adequate teaching resources. Furthermore, the participants contend that mastery of content and delivery entails knowing the curriculum and their students' various age-appropriate learning difficulties; for effective lesson delivery. Moreover, the learning of mathematics needs to be student-centred, with an emphasis on group work, for the mutual and collaborative building of new knowledge on existing knowledge, under the educator’s guidance. The study's findings also showed that Grade 12 Mathematics content is abstract therefore, subject educators should facilitate learning through a more concretised approach using realistic scenarios that appeal to the cognitive structures of individual students. Based on the findings, the study suggests that problem-based learning is the preferred instructional approach to teaching and learning Grade 12 mathematics and educators require development in their professional and content capacity in the use thereof.