Chronic kidney disease (CKD) and its treatment with hemodialysis pose significant challenges to patients' psychological well-being and adherence to complex treatment regimens. This randomized controlled trial investigated the effects of nurse-led, mindfulness-based interventions on psychological well-being and treatment adherence in patients undergoing hemodialysis. Eighty patients from a single dialysis center in Türkiye were randomly assigned to either an intervention group (n = 40) receiving six weekly mindfulness sessions or a control group (n = 40) receiving routine care. Data were collected using the Mindful Attention Awareness Scale (MAAS), the Psychological Well-Being Scale (PWB), and the End-Stage Renal Disease Adherence Questionnaire (ESRD-AQ) at baseline and post-intervention. Mixed-design analyses revealed significant improvements in mindfulness, psychological well-being, and all subscales of treatment adherence-including hemodialysis attendance, medication adherence, fluid management, and dietary compliance-in the intervention group compared to the control group (p \< 0.001). Moderate to large effect sizes (Cohen's d = 0.36-1.70) indicate clinically meaningful changes. Pearson correlation analysis demonstrated a positive association between psychological well-being and treatment adherence (r = 0.302, p \< 0.01). These findings suggest that structured, nurse-delivered mindfulness programs can simultaneously enhance psychosocial outcomes and adherence behaviors in hemodialysis patients. Integrating mindfulness-based interventions into routine nursing care may provide dual benefits by promoting emotional well-being and supporting self-regulated adherence to treatment regimens. Future research should explore long-term effects, broader patient populations, and the interplay between mindfulness, self-efficacy, and other psychosocial variables to further inform patient-centered hemodialysis care.