The main objective of this study is to compare the process of the senior secondary school mathematics curricula development in Ethiopia and Australia. The study was investigated qualitatively with document analysis and semi-structured interview research methods. The documents were collected from Federal Democratic Republic of Ethiopia Ministry of Education website and Australian curriculum website. The documents were analyzed and supported by interviews. The study was conducted based on four themes needs assessment, developing/writing the curriculum, implementation, and monitoring and evaluation. The study revealed both similarities and differences. The considerable differences in the senior secondary school mathematics curriculum development process are (1) emphasis given to international research results and contemporary issues on mathematics education as inputs for curriculum development (2) the underlying principle of content standard organizations (3) trialing the curriculum before implementation initiated, and (4) monitoring and evaluation strategies. Even though substantial differences exist, the similarities are (1) conducting needs assessment and (2) the adoption of the constructivism approach. Depending on the findings of the study, the suggested recommendations were presented under conclusion section.