OBJECTIVE: To test the feasibility and effectiveness of a mindfulness-based intervention in rural-to-urban migrant Chinese children using trained community volunteers. METHOD: Migrant students ages 9 to 16 from 5 schools in Shanghai (N = 653) were randomly assigned to a mindfulness only group (n = 167), a mindfulness plus life skills group (n = 118), or a waitlist control group (n = 368). The first 2 groups received an 8-week mindfulness intervention delivered 1 hour weekly by trained community volunteers. The mindfulness plus life skills group received 8 additional hours of skills-based mentorship. Measurements on mindfulness, resilience, and anxiety and depression symptoms were collected before and after intervention. Multivariable regression analyses compared the intervention vs control groups. RESULTS: Before intervention, there were no significant demographic or outcome measure differences between groups except that students in the intervention groups were slightly older. Students had relatively low levels of mindfulness and prosociality difficulties and similar degrees of depression and anxiety symptoms compared with prior studies. After intervention, no statistically significant differences were found in mean scores for mindfulness, resilience, anxiety, or depression in the intervention vs control groups. CONCLUSION: A volunteer-led mindfulness intervention did not significantly benefit migrant Chinese children after 8 weeks. More implementation research is needed for low-cost, scalable, and contextually effective mental health prevention programs. CLINICAL TRIAL REGISTRATION INFORMATION: Planting Seeds for Resilience-a Pilot Mindfulness and Mentorship Program in Migrant Chinese Children; http://www.chictr.org.cn; ChiCTR2100012027. DIVERSITY & INCLUSION STATEMENT: We worked to ensure that the study questionnaires were prepared in an inclusive way. We worked to ensure sex and gender balance in the recruitment of human participants. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented racial and/or ethnic groups in science. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.