The Katarungang Pambarangay Law (KPL) was institutionalized to promote peaceful dispute resolution at the community level, reduce court congestion, and ensure the speedy administration of justice. This study assessed the effectiveness of the Katarungang Pambarangay Law in the administration of justice in selected barangays of Cabanatuan City. Using a quantitative research design, data were gathered from Punong Barangay and Lupon Tagapamayapa members through structured questionnaires. The data were analyzed using descriptive statistics, particularly the weighted mean, based on a five-point Likert scale. Findings revealed that KPL is highly effective in resolving disputes at the barangay level, ensuring speedy disposition of cases, and decongesting court dockets, with an overall weighted mean of 4.69 interpreted as Strongly Agree. Respondents strongly affirmed that KPL promotes amicable settlement, reduces litigation time, and supports judicial efficiency. Despite its effectiveness, the study recognizes the need for continuous capacity-building to prevent procedural lapses, particularly the premature issuance of Certificates to File Action. In response, a community extension project titled “Strengthening Barangay Justice Through Capacity-Building: A Mandatory Training Program for Lupon Tagapamayapa Members” is proposed to enhance the competence, compliance, and effectiveness of barangay justice implementers, thereby sustaining the objectives of the Katarungang Pambarangay Law.