The aims of this study were to (1) identify and categorize study eligibility criteria concepts used in cancer nursing randomized controlled trials and (2) determine the extent to which a previously identified set of study eligibility criteria, based primarily on medical randomized controlled trials, were represented in cancer nursing randomized controlled trials. A total of 145 articles of cancer nursing randomized controlled trials indexed in PubMed or Cumulative Index to Nursing and Allied Health Literature and published in English from 1986 to 2010 were screened, and 114 were eligible. Directed content analysis was conducted until data saturation was achieved. Forty-three concepts categorized into eight domains were extracted from 49 articles published in 27 different journals. Most of the concepts identified were related to health status, treatment, and demographics domains. Although many concepts matched to the previously identified study eligibility concepts based on medical research, new concepts may need to be added to fully represent cancer nursing research. This study provides a solid foundation for future study of mapping the concepts to existing standardized terminologies to identify which systems can be adopted. Nursing researchers can use these eligibility criteria concepts as a guideline in structuring the eligibility criteria for their studies.