In the 2019 cycle of the Trends in International Mathematics and Science Study (TIMSS), the Western Cape Education Department (WCED) sought more precise provincial achievement estimates and therefore increased the provincial sample size from 30 to 150 schools at the Senior Phase (Grade 9). The data from the Western Cape sample forms part of the overall South African results, and is also reported separately as a self-standing entity called a 'benchmarking participant' in the international TIMSS report. Participation in TIMSS allows countries and benchmarking participants to evaluate their learners' achievement and monitor the health of their education systems over time. TIMSS also allows participants to compare their achievement with other participants. In addition, the study allows the exploration of how contextual factors are associated with mathematics and science achievement. In August 2019, the Human Sciences Research Council collected achievement and contextual data in 149 secondary schools from 149 principals, 170 mathematics educators, 162 science educators, and 5 351 Grade 9 learners in the Western Cape. The analysis of data was informed by a framework focused on how to build achievement and bridge achievement gaps. The results of the Western Cape analyses are presented in this publication.