Introduction: Nursing-sensitive indicators (NSIs) measure factors influencing nursing care quality and patient outcomes. Established NSIs reflect general and select specialty nursing practices. However, a core set of NSIs for international pediatric oncology nursing practice does not currently exist. Without valid and reliable quality indicators, the impact of nursing care on children and adolescents with cancer cannot be effectively measured and improved. The purpose of this study was to develop a preliminary core set of NSIs for international pediatric oncology nursing that would be important, actionable, and feasible to measure across varied resource settings and countries. Design/Methods: A multiphase sequential mixed methods research design, intersected with a classical Delphi method, was utilized. Through purposive snowball sampling, 122 expert pediatric oncology nurses from 43 countries participated. Round One: Panelists identified five potential NSIs and constructs. Open-ended responses were coded and categorized through descriptive content analysis and integrated into the next round. Round Two: Panelists selected their top 10 NSIs and constructs and ranked them by importance to patient care quality. Mean importance scores were calculated through reverse scoring; the top 10 NSIs and constructs were integrated into the next round. Round Three: Panelists ranked the top 10 NSIs and constructs by order of importance for this particular population, then rated each NSI/Construct for actionability and feasibility of measurement by Likert-scale. Rounds Two and Three were analyzed using descriptive statistics. Mixed methods meta-inferences were derived from the integration of Rounds One and Three findings. Results: Eighty-five (70%) panelists from 38 countries completed all Delphi survey rounds. The preliminary core set of NSIs and constructs identified by the expert panel, and ranked in order of importance, were as follows: safe chemotherapy administration and handling, infection prevention/control, pediatric oncology nursing orientation program, early warning score system/recognition of patient deterioration, chemotherapy/biotherapy education/course, pain assessment/management, symptom assessment/management, patient and family education, palliative/end of life care, and continuing nursing education/competency. All NSIs and constructs were rated as actionable; all but palliative/end of life care were rated as feasible to measure. Each of the 10 NSIs and constructs were nominated in Round One by at least one expert panelist from low- and middle-income and high-income countries, and at least one panelist from the Americas. Conclusion: Preliminary core NSIs and constructs provide insight into common attributes of international pediatric oncology nursing practice that are important, actionable, and feasible for quality measurement. Clinical Relevance: NSIs have the potential to drive quality improvement, guide comparison with other institutions, promote knowledge-sharing, and advance pediatric oncology nursing outcomes around the world. These NSIs and constructs may also be relevant to other pediatric and adult oncology settings.