Background: To inspire excellent clinicians to become educators, the role of the nurse educator needs to be more fully defined. Capabilities rather than competencies may better describe advanced professional practice.Objectives: To develop an effective measure of the multifaceted complexity of the nurse educator role, which will enable nurse educators to (1) self-assess their capability set, (2) identify areas for professional development and (3) evaluate professional development interventions.Method: A questionnaire (with 6 subsets) interrogating nurse educator capabilities was developed through wide professional consultation and an expert working group, and evaluated. Statistical analyses investigated internal consistency, internal correlation of items, relationship to professional practice data (also collected via questionnaire) and test-retest reliability of the questionnaire and subsets.Participants: Nurse educators (266) working within universities and health services in Australia and New Zealand.Results: Analyses resulted in a 93-item Capabilities of Nurse Educators (CONE) questionnaire, with six subsets measuring Teaching Knowledge and Practice, Drawing from Nursing Knowledge, Teaching Relationships, Leadership, Research Orientation and Research Action. The questionnaire and subsets demonstrated internal validity (Cronbach’s α ≥ .9). Reliability in this population was supported via significant differences between ranked questionnaire scores in ordinal categories of data collected about professional practice. The 8-week test-retest analysis supported the reliability of the CONE over time and suggested the questionnaire could be useful to evaluate the success of professional development activities.Conclusions: The CONE questionnaire proved useful for measuring the complex capabilities of nurse educators in the academic and health service contexts studied, and may assist educators to self-assess their capability sets and identify areas for professional development. It also shows promise as an evaluation tool for professional development. The utility of CONE as a self-diagnostic tool in career advancement, particularly in novice educators and educators outside Australia, requires further confirmation.