The poor performance of South African learners in Mathematics in recent national and inter-national benchmark tests is concerning. Literature have repeatedly shown a link between the mathematical content knowledge (MCK) of teachers and the performance of the learners they teach. In an attempt to update and improve Curriculum 2005 (1997-2010), the National Curriculum Statement (NCS) was introduced in 2011. NCS included the Curriculum and Assessment Policy Statement (CAPS), which stipulates content to be taught as well as how it should be assessed in terms of four cognitive levels. CAPS included some previously non-compulsory topics (for example probability) which used to be part of Paper 3 in Curriculum 2005. This study examined the MCK of teachers (𝑛=8) on the topic of probability in relation to the performance of the Grade 11 (𝑛=89) and Grade 12 (𝑛=75) learners on the same topic. The MCK of the teachers was examined by investigating their qualifications, years of experience in teaching mathematics, professional development sessions (organised by the Gauteng Department of Education) they were involved in, as well as examining written responses on examination-type questions on probability (Test 1). The learners’ performance was examined by investigating their written responses on the topic of probability in the final Grade 11 examination (November 2013) and the Grade 12 preparatory examination (September 2014). The poor performance from both teachers and learners was a matter of concern regarding teachers’ MCK. Even though the teachers were all qualified (all had a teaching diploma or a degree), they only managed to score and average of 73% on Test 1. The teacher with the most teaching experience performed the best in the test, showing a strong MCK. The teachers felt that the professional development sessions that they attended did not contribute to the improvement of their MCK on probability. The performance of the learners with regard to probability was consistent with the poor performance of learners in mathematics benchmark tests, and they only managed to score an average of 48% in Grade 11 and a shocking 30% in Grade 12.