Informed by the research of the first author for his doctoral thesis “Cooperation, Complexity and Adaptation: Higher Education capacity initiatives in international development assistance programmes in sub-Saharan Africa” (2018), this paper examines Irish Aid funded initiatives in mathematics education (at primary, post-primary and third levels) in Tanzania in the 1990s. Testimonies of key informants (both Tanzanian and Irish) involved in these initiatives, along with unpublished archival material from the period, provide the evidence base for the qualitative research. The research methodology employed was inductive analysis and purposive sampling. The second author worked on a project supporting mathematics (and mathematics education) in both the university and NGO sectors in Tanzania from 1991 to 1994. The authors argue that, in a development context, initial and continuing mathematics teacher education requires a whole-of-systems perspective, considered over an extended period of time and transcending the boundaries between levels of education.