This study aimed to identify the barriers and promoters for participation in cancer treatment decision in the era of shared decision-making (SDM) process. A qualitative design was utilized. Nineteen nurses and 11 nurse practitioners from oncology inpatient and outpatient settings participated in semi-structured interviews. Data were analyzed using directed content analysis. The findings include practice barrier, patient barrier, institutional policy barrier, professional barrier, scope of practice barrier, insurance coverage barrier, and administrative barrier. Multidisciplinary team approach, having a nursing voice during SDM, high level of knowledge of the disease and treatment, and personal valuation of SDM participation were perceived as promoters. Oncology nurses and nurse practitioners face many barriers to their participation during SDM. Organizational support and system-wide culture of SDM are essential to achieve better cancer treatment decisions outcome. Additional studies are needed to determine the factors that can promote more participation among nurses and nurse practitioners.