Migrant children are more likely to experience challenging circumstances and exhibit greater emotional and behavioral difficulties than native children. Nowadays, mindfulness training (MT) has been employed as a means of enhancing health-related outcomes in children and adolescents, with promising results. The present study employed a randomized controlled trial to investigate the impact of 6 weeks of MT on mindfulness, inner peace, mind wandering, and emotion in migrant children. Ninety-two migrant children with a mean age of 9.74 ± 0.96 years, ranging from 8 to 11 years, participated in the study. Participants were randomly assigned to either the MT or control (CON) group, with their final exam scores being balanced. In the end, 46 children participated in the MT group, and 46 children participated in the CON group. Participants in the MT group received MT for 6 weeks with 2 sessions per week (20 min/session). Students in the CON group completed academic self-study during the same time period. Participants completed the Mindful Attention Awareness Scale--children, the Peace of Mind Scale, the Positive and Negative Affect Scale, and the Mind Wandering Questionnaire before and after the 6 weeks. MT significantly improved the migrant children's mindfulness and peace of mind and reduced negative affect and mind wandering. This study made a significant contribution to the feasibility and efficacy of MT in migrant children.