Given the impact of international large-scale assessments (ILSAs) on policy-making in different educational systems around the world, this study aims to examine whether national mathematics curricula in different educational systems harmonize over time. Data from the Trends in International Mathematics and Science Study (TIMSS) is used to explore this issue. In addition to background questionnaires given to students, teachers and schools, a curriculum questionnaire was completed by each national research coordinator (NRC) in all participating countries in each TIMSS cycle. In the present study, data from 2003, 2007, 2011 and 2015 was used. The analyses focused on the information about the extent to which the national mathematics curriculum covered certain topics in the subdomains of mathematics tested in TIMSS Grade 8. Growth curve modeling and latent profile analyses were applied to uncover the development trend and countries’ unobserved profiles in mathematics content domains of Number, Algebra, Geometry, and Data. Three clusters of countries were identified. Most countries belonged to the same profile in the later cycles of TIMSS. The study found indications of a general harmonization with respect to number of topics covered in countries’ curricula over time, thus contributing to discussions of policy implications of a global curriculum.