This research examines the complex dynamics involved in forming and maintaining a relationship with the natural world. In the context of increasing urbanisation, environmental degradation, and digitalisation, there is a growing need to understand how human–nature relationships are conceptualised, developed, experienced, maintained and measured. Added to this complex relationship is the unprecedented implications of a global pandemic, and strict lockdown restrictions. Although connection with nature has been associated with benefits for human wellbeing and pro-environmental outcomes, less attention has been given to the quality of this relationship and to the possibility that human–nature relationships may include ambivalent, difficult, or negatively valanced dimensions. The research was conducted across four sequential stages, guided by a modified-Delphi methodology. These stages aimed to develop a deeper understanding of the human–nature relationship in light of current society, build consensus on its core components, and use co-productive methods to develop a robust and representative measure of relationship quality. Findings from the qualitative phase indicated that the human–nature relationship may be understood as a transactional process shaped by elements of shared identity, respect, care, and meaningful engagement. Importantly, expert and expanded-expert perspectives also suggested that this relationship is not always wholly positive, but may involve risk, vulnerability, discomfort, and other challenging relational experiences. Building on these findings, a dedicated working group, consisting of experts in the areas of nature and scale validation, developed a preliminary 13-item Quality of Human–Nature Relationship Measure. Initial analyses indicated good internal reliability and validity. The measure captures dimensions including self-identification with nature, respect for nature, perceived risks associated with nature exposure, and longing for nature in its absence. The measure is described as preliminary because further validation and refinement are needed, particularly in relation to the potential subscales identified during factor analysis. Nevertheless, the findings offer an important contribution to human–nature relationship research and provide a foundation for future work by researchers, practitioners, and policymakers interested in strengthening relationships between people and the natural world.