Although collaboration is an intensive way of working together, it is essential for such efforts to achieve shared goals. Health technology assessment (HTA) is transdisciplinary and has an important history of collaboration, with collaboration featuring increasingly in the strategic plans of HTA bodies and stakeholders. Collaboration can be between HTA bodies and between HTA bodies and other stakeholders—most notably regulators but increasingly payers, patient and caregiver organizations, clinicians–clinical societies, and academia. The 2024 HTAi Global Policy Forum (GPF) discussed collaborations involving HTA bodies, reviewing existing and previous collaborations to see what has worked and what can be learned. Core discussion themes included: (i) determining the collaboration purpose is essential but may be dynamic, changing over time; (ii) choosing the collaboration topic takes time, requiring upfront investment and stakeholder mapping; (iii) inviting the right participants and treating them equally is important, including those who can impact HTA, those who will be impacted by HTA and those who bring new information; (iv) collaborations need clear governance, defined roles, responsibilities, metrics, and case study–pilots can be a useful operational model; (v) resourcing collaborations sustainably is a challenge—the time, people, and money required are often under-estimated; (vi) undertaking continual, iterative learning reviews ensures ongoing value and impact of collaborations. Recommendations for future work include the development of a “go/no-go” checklist to determine when collaboration is needed, supplemented with a set of “best practice” principles for establishing and working in collaborations involving HTA bodies.