BACKGROUND: Nurses experience various health-related issues due to the nature of their work. AIM: This study aimed to examine the effect of a mindfulness-based intervention on stress overload, depression and mindfulness among nurses. A secondary objective was to examine the role of the setting (i.e., in and out of the hospital as a natural setting) on mindfulness-based intervention effectiveness. METHODS: A randomized controlled trial with three groups' pretest-posttest design was used in this study. A total of 195 nurses were recruited-65 intervention-inside hospital, 60 intervention-outside hospital, and 63 control. The mindfulness-based intervention was delivered by a certified mindfulness practitioner over 4 weeks in Jordan. Data were collected using a demographics questionnaire, the Stress Overload Scale Short, the Center for Epidemiologic Studies Depression Scale-Revised, and the Five Facet Mindfulness Questionnaire. RESULTS: Multivariate analysis showed a statistically significant effect of the intervention on the linear combination of the dependent variables V = 0.44, F[6, 368] = 17.56, p < .001. Follow-up analyses showed that a mindfulness-based intervention significantly decreased stress overload, depression, and increased mindfulness levels among nurses in intervention groups compared with the control group. In addition, conducting a mindfulness-based intervention outside the hospital has a better effect on mindfulness levels than the inside hospital. LINKING EVIDENCE TO ACTION: The effect of a mindfulness-based intervention on stress overload, depression, and mindfulness should be considered when planning for nurses' well-being and the quality of care provided. Nurse managers are encouraged to use the study's findings to promote nurses' well-being.