This study aimed to investigate the necessary teaching competencies for early career mathematics teachers and identify the degree to which these competencies are represented in pre-service teachers' preparation programs. The study also aimed to identify the most effective teaching strategies that should be included in preparation programs. The study was applied to (142) early career mathematics teachers in Jordanian public schools with no more than three years of experience. The study relied on a mixed methodology based on quantitative and qualitative approaches. A questionnaire and semi-structured interviews were used to collect the data. The study concluded that teaching competencies fall within four areas: namely, knowledge competencies, implementation competencies, assessment competencies, and personal competencies. The pre-service preparation programs succeeded in preparing mathematics teachers well by acquiring these competencies and providing them with personal skills that provide them with effective and continuous communication with their students. Mathematics teachers find that the most effective teaching strategies are those that focus on students' interests and that the infrastructure and capacity of the classrooms have a major role in limiting the ability of mathematics teachers to apply what they have learned in the preparation programs. Mathematics teachers recommend that graduates who enter the teaching profession should pay attention to continuous improvement by enrolling in courses that enable them to keep pace with cognitive, professional, and technical developments in mathematics. Keywords: pre-service preparation programs, early career mathematics teachers, teaching competencies, teaching performance.