Background <p>Although sibling rivalry is a normal part of development, in high-stress or dysfunctional families it can become a chronic stressor that is associated with increased maternal distress. This scoping review mapped the available evidence on the associations between sibling rivalry or conflict, and maternal mental health, including proxy indicators, in these contexts.</p> Methods <p>Following the Population-Context-Concept framework and PRISMA-ScR guidelines, a search of PubMed and PsycINFO was conducted for studies published between 2010 and 2024 that reported on sibling rivalry, conflict, or relationship quality alongside maternal mental health or clearly defined proxies. Two reviewers independently screened, charted, and thematically synthesized the eligible studies.</p> Results <p>Eleven studies met the inclusion criteria, comprising cross-sectional surveys, longitudinal cohorts and interventions, primarily from high-income settings. Sibling aggression, bullying and antagonism were found to be linked with a number of factors, including poverty, large families, step- or blended families, care demands and harsh or low-warmth parenting. Maternal mental health was assessed directly in few studies, being more often inferred from parenting stress, caregiver burden, or conflictual parent-child relationships. Evidence from longitudinal and intervention studies suggested interdependent, bidirectional links between sibling adjustment and maternal distress.</p> Conclusion <p>Mothers are rarely the focus of attention in the study of sibling conflict, despite the fact that current evidence places it within a broader context of family stress. Theory-driven longitudinal research and trials that measure and target maternal mental health within sibling and family systems interventions are therefore needed to inform more holistic practice.</p>