Background <p>Environmental constraints pose significant challenges to oral care provision by intensive care unit (ICU) nurses. However, the specific impact of these constraints on role conflict and role ambiguity in oral care practice remains underexplored. Such role stress can threaten both patient safety and nurses’ psychological well-being. Therefore, this study aimed to address this gap by examining the role stresses of ICU nurses through the lens of role theory.</p> Methods <p>A descriptive qualitative study design was used. Using purposive sampling, 16 nurses from three ICUs at two tertiary hospitals in China were recruited for semi-structured interviews. Guided by role theory, data analysis was performed using a directed content analysis approach that combined both deductive and inductive strategies.</p> Results <p>Through the lens of role theory, role ambiguity and conflict emerged as core findings, closely intertwined with role overload and underqualification. Role ambiguity was driven by four interrelated factors: failed preparation, informal alliances, responsibility vacuum, and subjective assessment. Meanwhile, role overload, hierarchical culture, and interpersonal risks collectively contributed to ethical trade-offs and silent complicity. The study further identified nuanced variations in these role stresses influenced by seniority levels and specific types of ICU units.</p> Conclusion <p>The role ambiguity and conflict experienced by ICU nurses are not individual failures, but systemic products of environmental constraints. Effectively mitigating these role stresses requires a fundamental redesign of the role environment, including the establishment of interprofessional protocols to clarify boundaries, the integration of objective tools to define performance, and the cultivation of a psychologically safe culture to empower voice. These systemic reforms are essential to safeguard both patient safety and the well-being of nurses.</p> Trial registration <p>Not applicable.</p>