Alumni engagement has increasingly become an important strategy for enhancing institutional sustainability, strengthening university–stakeholder relationships, and promoting resource mobilisation in higher education. Despite its recognised benefits, alumni engagement remains underdeveloped in many universities in Uganda, where institutional mechanisms for cultivating long-term relationships with graduates are still evolving. This study examined the rationale for alumni engagement and explored the modes through which alumni engagement is implemented in universities in Uganda. A qualitative multiple case study design was employed involving eleven purposively selected participants comprising one Academic Registrar, two Alumni Relations Officers, two officials from alumni associations, and six active alumni drawn from three universities in Uganda. Data were collected through semi-structured interviews and document analysis and analysed using inductive thematic analysis following Braun and Clarke's six-phase framework. The findings revealed that alumni engagement is primarily undertaken to advance institutional missions, cultivate lifelong relationships with graduates, strengthen university governance, enhance student experiences, and mobilise financial and non-financial resources. Four overarching themes emerged from the analysis: communication, networking, fundraising, and infrastructure development. Universities engage alumni through social media platforms, alumni databases, newsletters, reunion events, alumni chapters, mentorship programs, volunteering, donations, outreach initiatives, and endowment fundraising. These strategies not only strengthen alumni identity and institutional loyalty but also facilitate resource mobilisation and knowledge sharing that support institutional development. The study concludes that meaningful alumni engagement extends beyond fundraising to encompass lifelong partnerships that enhance institutional sustainability and graduate participation in university development. The study recommends that universities institutionalise comprehensive alumni engagement policies, strengthen alumni information management systems, improve student experiences as a foundation for future alumni loyalty, establish vibrant alumni chapters, and diversify alumni fundraising and investment initiatives to promote long-term institutional sustainability.