A new two-year Post University Specialty Training (PUST) programme in family medicine was introduced to improve the quality of postgraduate speciality medical education in Tajikistan. Postgraduate education of family doctors (FDs) needs to be urgently scaled up, as 38% of FD positions in Tajikistan remained unfilled in 2018. Moreover, the international financial support for the PUST programme is ending. This investment case assesses the minimum funding needed for the continuation and scale-up of PUST and establishes the rationale for the investment in the light of a recent evaluation. Methods: The costs of the programme were calculated for 2018 and a scale-up forecast made for the period 2019–2023. The impact of the scale-up on the shortage of FDs was assessed. An evaluation using a Multiple Choice Questionnaire and Objective Structured Clinical Examination (OSCE) assessed and compared theoretical knowledge, clinical skills and competencies of PUST trained and conventionally trained FDs. Results: The annual costs of the programme were US$ 228,000 in 2018. The total investment needed for scaling up PUST from 31 new FDs in 2018 to 100 FD graduates each year by 2023 was US$ 802,000.However, when the retirement of FDs and population growth are considered, the scale-up will result only in maintaining the current level of FDs working and not solve the country’s FD shortage. The PUST FDs demonstrated significantly better clinical skills than the conventionally trained interns, scoring 60 and 45% of OSCE points, respectively. Theoretical knowledge showed a similar trend; PUST FDs answered 44% and interns 38% of the questions correctly. Conclusions: The two-year PUST programme has clearly demonstrated it produces better skilled family doctors than the conventional one-year internship, albeit some enduring quality concerns do still prevail. The discontinuation of international support for PUST would be a major setback and risks potentially losing the benefits of the programme for family medicine and also other specialities. To guarantee the supply of adequately trained FDs and address the FD shortage, the PUST should be continued and scaled up. Therefore, it is essential that international support is extended and a gradual transition to sustainable national financing gets underway.