UNLABELLED: WHAT IS KNOWN ON THE SUBJECT?: Despite the increased interest in nursing students' happiness in South Korea, few studies have attempted to identify factors influencing their happiness. Therefore, nursing educators should consistently investigate the factors influencing happiness and develop strategies to improve happiness among Korean nursing students. WHAT THIS PAPER ADDS TO EXISTING KNOWLEDGE?: This study confirmed that there were positive correlations between grateful disposition, social support and happiness. In addition, grateful disposition and support from intimate people were identified as predictors of happiness in Korean nursing students. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Development of intervention programmes to help nursing students increase grateful disposition and support from intimate people may be helpful for improving happiness. These programmes can include activity, such as writing a gratitude journal, and extracurricular programmes, such as mentoring programmes between seniors and juniors and/or professor and student. ABSTRACT: Introduction Happiness is very important in the training and development of nursing students as future nurses. However, nursing students experience a high level of stress and low level of happiness in South Korea. Aim This study aimed to investigate factors that affect happiness among nursing students in South Korea. Method Data were collected from a total of 241 nursing enrolled in two 4-year baccalaureate nursing programmes in South Korea, using a self-administrated questionnaire. To identify predictors of happiness, stepwise regression analysis was conducted. Results The results indicated that grateful disposition and support from intimate people significantly predict happiness among Korean nursing students. These two factors accounted for 38.0% of the variance in happiness. Discussion This study indicated grateful disposition and support from intimate people as factors promoting happiness in nursing students. The findings highlight grateful disposition and support from intimate people as important factors when developing effective interventions that foster nursing students' happiness.