A National Wellbeing Project was developed following COVID-19 to promote wellbeing in children and young people (CYP). Two 8-week, awareness-based interventions, Breath-Body-Mind (BBM) and Creative Mindfulness (CM), were delivered by external facilitators over an 8-week period in primary and post-primary schools across 5 sites in the Republic of Ireland. A convergent mixed methods evaluation was conducted. Teachers completed the Emotional Regulation Checklist for CYP before and immediately post intervention. Focus groups and interviews were conducted with 40 CYP, 13 school staff and 6 programme staff. Linear mixed modelling showed a main effect of intervention on teacher reported (n = 172) emotional regulation and dysregulation in children; post-hoc test showed significant changes amongst those who engaged in BBM only. Stakeholders highlighted positive experiences of programme participation and intervention benefits, including new coping skills and improved regulation in classroom settings. Capacity building benefits for teachers and schools were also identified. The qualitative findings shed light on facilitators and challenges to programme success. Mental health challenges in CYP have increased post-COVID-19. The findings point to the potential utility of brief wellbeing-focused supports in promoting regulation and wellbeing in CYP, although further research is required. Factors influencing the success of school-based wellbeing interventions are discussed.