Similar to counties such as the U.K. and the U.S.A, the Irish education system is divided into four key stages; pre-school education, primary level education, second level education and tertiary education. Transition between each of these phases has its own set of challenges but many believe the most challenging of all is the transition from primary to second level education. This quantitative, national study investigates the transition from primary to second level mathematics education from the perspective of teachers. It investigates sixth class teachers’ knowledge of the mathematics curriculum and teaching strategies employed in first year of second level and first year mathematics teachers’ knowledge of the mathematics curriculum and teaching strategies favored in sixth class. The results of the study highlight low levels of knowledge in these domains among both sixth class and first year mathematics teachers. The ramifications of this gap in teacher knowledge is also discussed in detail.