Background <p>Intensive Care Unit (ICU) nurses are frequently exposed to sudden patient deaths and are often the first professionals to interact with bereaved families. Providing grief counseling for family members in the context of unexpected death presents unique emotional and professional demands on ICU nurses, who are often the primary providers of bedside care and family support. Although grief support has received growing attention in pediatric and palliative nursing, the role of nurses in delivering grief counseling for family members following unexpected adult death in ICUs remains underexplored, particularly in the Chinese cultural context. In this study, the COM-B (Capability–Opportunity–Motivation–Behavior) model was used to examine factors affecting ICU nurses’ grief counseling behaviors toward family members.</p> Methods <p>An exploratory qualitative study was conducted using semi-structured interviews at a tertiary hospital in East China. Purposive sampling was used to recruit registered ICU nurses with at least a bachelor’s degree, one year of clinical experience, and prior experience in providing grief counseling for family members. Data were analyzed using directed content analysis guided by the COM-B framework with NVivo 11 software.</p> Results <p>Seventeen ICU nurses participated in this descriptive study. Directed content analysis identified three major themes and eleven subthemes affecting behaviors of grief counseling for family members: capability factors (inadequate grief-related knowledge, deficits in communication skills, and limited emotional self-regulation), opportunity (promotion of humanistic care initiatives, strong external support, sociocultural norms, and unit’s grief-support culture), and motivational factors (professional value, self-efficacy in grief counseling for family members, attitude toward and willingness to provide counseling, and empathy awareness and development). The elements interacted in complex ways, jointly shaping whether nurses were able, willing, and confident to provide grief counseling for family members after unexpected deaths.</p> Conclusions <p>ICU nurses’ grief counseling for family members after unexpected patient death is a complex behavioral process, shaped by internal competencies, external conditions, and cultural norms. Strengthening this practice likely requires targeted education to fill in knowledge and communication gaps, supportive organizational cultures that empower nurses, and strategies that enhance professional identity and motivation. Given the exploratory design and relatively small sample size, these findings must be interpreted with caution. Ultimately, these insights underscore the critical role of nurses in grief support and call for context-sensitive interventions to improve grief care in acute settings.</p>