While a growing number of works have been published about the use of mixed methods research in nursing, scarce attention has been devoted to the issue of the quality of mixed methods within the discipline. The quality appraisal of mixed methods research poses two problems to nursing science: first, current quality criteria are not nursing-specific and consequently, they might not facilitate the application of mixed methods research findings into nursing practice. Second, criteria were theoretically derived and as such, they might not faithfully account for the decisions that nurse researchers take when appraising mixed methods research studies. This qualitative, within-case study explored the views of nurse researchers about mixed methods research in general and, more specifically, the question of quality in mixed methods research. An international sample of 13 nurse researchers was interviewed via Skype and phone. Thematic analysis revealed that the participants favored universal, cross-disciplinary quality criteria, and not criteria specific to the nursing discipline, and a consensual and standardized approach to appraising the quality of mixed methods research. Recommendations are put forward to strengthen the quality appraisal of mixed methods research studies by nurse researchers, as well as future works on this topic within nursing science.