Background: Ethics development is one of the most important aspects of professional practice in health sciences students. Understanding factors affecting ethics development can enhance clinical and professional performance in students. Objective: This study was conducted to explore students’ perceptions about factors affecting professional ethics development. Research design: This study is a conventional content analysis. Data were collected through 20 semi-structured interviews and two focus group interviews (12 students) during 2017–2018. Data were analyzed concurrently with data gathering, using the conventional content (...) analysis approach of Graneheim and Lundman. Participants and research context: In total, 8 students of nursing, 5 medical students, 4 students of anesthesia and 3 operating room students in individual interviews, and 12 students in two focus group interviews from one university in the south of Iran were selected through purposive sampling. Ethical considerations: The research was approved by the Ethics Committee of one university in the south of Iran. Findings: The findings revealed two themes: personal and background factors. Personal factors consisted of the two categories of individual motivation and tendencies and interpersonal interactions. Background factors consisted of the two categories of role and function of teachers and environmental agents. Discussion and conclusions: According to the findings, both background and individual factors affect development of professional ethics in students. Understanding these factors along with reinforcement of educational planning in this field can improve healthcare services. (shrink)