Border insecurity in fragile tri-border regions persists due to weak governance, high cross-border mobility, and complex socio-economic interdependence. This study examined the influence of Local Peace Committees (LPCs) on Border Security Management (BSM) in the Mandera Triangle, a border region shared by Kenya, Ethiopia, and Somalia. It evaluated the contribution of LPCs to reducing cross-border incidents, improving the safety of movement, curbing illegal activities, strengthening institutional trust, and sustaining cross-border economic interactions. A convergent parallel mixed-methods design was employed, integrating quantitative survey data from 393 respondents with qualitative evidence from 16 key informant interviews and two focus group discussions involving 6-10 participants each. Data were analyzed using descriptive statistics, bivariate regression, and thematic analysis to ensure comprehensive interpretation and triangulation of findings. The results indicate that LPCs have a significant positive contribution to BSM. Findings revealed that LPCs improve conflict mediation, enhance community-based early warning systems, and strengthen trust between local communities and formal security institutions. Regression analysis established a strong positive relationship between LPCs and BSM outcomes. The study concludes that sustainable border security in the Mandera Triangle requires integrating community-based peacebuilding mechanisms with state-led security approaches. It recommends institutionalizing LPCs within Kenya’s border security framework, providing sustainable funding, strengthening early warning and response capacities, and promoting the active participation of women and youth to enhance long-term peace, stability, and security.