Understanding the pandemic's impact on individuals and communities, expanding affective-social support networks, and strengthening family and community bonds are crucial strategies for promoting children's mental health and resilience, as these factors foster social and psychological resources for coping with adversity. This study aimed to adapt and evaluate the effectiveness of a psychosocial intervention targeting children who experienced adverse events related to the COVID-19 pandemic. Conducted in Brazil, this quasi-experimental study employed a cross-sectional design integrating quantitative and qualitative methodologies to assess a program originally developed by Save the Children in Denmark. The Brazilian adaptation, Programa ConViVer, consisted of eight sessions. A total of 116 children aged 8-12 years (M = 9.8; SD = 1.1) were recruited and randomly assigned to an Experimental Group (EG; n = 69) or a Waiting Group (WG; n = 47), with 52.6% identifying as female. Participants were from five Brazilian cities: Belém, Brasília, Fortaleza, Porto Alegre, and São Carlos. Program effectiveness was assessed at pre-test (T1) and post-test (T2) using validated psychological instruments measuring depression, stress, affect, resilience, self-esteem, self-efficacy, and life satisfaction, along with field diaries. Statistical analyses characterized group performance across all measures and examined changes between T1 and T2 using robust t-tests for trimmed means in paired samples. Results showed that Programa ConViVer significantly increased positive affect and reduced indicators of negative affect, depression, and stress among EG participants. No significant changes were observed in the WG, confirming the intervention's effectiveness. Additionally, the program enhanced children's perceptions of their affective and social support networks—factors widely recognized as essential for promoting mental health and resilience in contexts of adversity. The dissemination of these findings may guide further research and support the replication of this intervention among children facing post-pandemic challenges.