Background: New Zealand recently introduced law permitting terminally ill people to request and receive assisted dying (AD) in specified circumstances. Given the nature and complexity of this new health service, research is vital to determine how AD is operating in practice. Objective: To identify research priorities regarding the implementation and delivery of AD in New Zealand. Methods: Using an adapted research prioritisation methodology, the researchers identified 15 potential AD research topics. A mixed-methods survey of health professionals was undertaken where respondents were asked to rate the 15 topics according to the relative importance for research to be conducted on each issue. Respondents could also suggest additional research areas, and were invited to participate in a follow-up interview. Results: One hundred and nineteen respondents completed the survey. 31% had some experience with AD. The highest rated research topic was the ‘effectiveness of safeguards in the Act to protect people’; the lowest rated topic was research into the ‘experiences of non-provider (e.g., administrative, cleaning) staff where assisted dying is being provided’. Respondents suggested 49 other research topics. Twenty-six interviews were conducted. Thematic analysis of interview data and open-ended survey questions was undertaken. Six research themes were identified: general factors related to the wider health system; the experiences of health care providers at the bedside; medico-legal issues; the impact of AD; experiences on the day of dying; and the overall effectiveness of the AD system. Key issues for stakeholders included safety of the AD service; ensuring access to AD; achieving equity for ‘structurally disadvantaged’ groups; and ensuring the well-being of patients, families/whānau, providers and non-providers. Conclusions: Based on early experiences of the implementation of the AD service, health professionals provide important insights into what research should be prioritised post-legalisation of AD. These findings can be used to shape the research agenda so that research may inform law, policy and best practice.