With the ratification of the UN Convention on the Rights of Persons with Disabilities (UNCRPD) in 2007, disability inclusion gained significance in international cooperation. Article 32 commits states to ensure inclusiveness and accessibility in development programmes. Despite ratification, implementation gaps persist, especially concerning the link between disability and poverty in the Global South. The WHO and World Bank highlight the “vicious cycle” of poverty and disability, though recent research questions its empirical basis. Nonetheless, more than one billion people live with disabilities, 80% in the Global South. Germany ratified the UNCRPD in 2009 and launched an Action Plan through BMZ to mainstream disability in German Development Cooperation (GDC). This led to a commissioned study and manual on disability inclusion by GIZ’s “Inclusion of Persons with Disabilities” sector programme, carried out by SLE, including fieldwork in Namibia. The study follows a twin-track approach, targeted measures and mainstreaming, and adopts the social model of disability. The field research focused on GIZ’s Vocational Education and Training (ProVET) and Transport programmes in Namibia. Findings show exclusion due to physical, attitudinal, and institutional barriers, despite existing frameworks. Recommendations include improving VET access, adapting transport infrastructure, awareness training, and integrating disability into engineering curricula. The resulting “Inclusion Grows” manual offers tools and knowledge for implementing inclusive practices. However, overburdening projects with mainstreaming demands should be avoided. Active participation of persons with disabilities in all project phases remains vital. Attitudinal change is essential to achieve full societal inclusion as envisioned by the UNCRPD.