Abstract: This study assessed the effect of supply chain integration practices on the operational efficiency of distribution firms in Rwanda, focusing on Sulfo Rwanda Industries. Specifically, the study examined the effect of internal integration on operational efficiency. A mixed-methods approach and descriptive correlational research design were adopted. The target population comprised 567 employees involved in supply chain and operational activities, from which a sample of 235 respondents was determined using Yamane’s formula. Stratified and simple random sampling techniques were used. Data were collected through structured questionnaires and interviews and analyzed using SPSS version 26. Descriptive statistics, Pearson correlation, and simple linear regression were employed. The findings revealed that internal integration positively contributes to operational efficiency. Respondents reported that sharing workflow systems, coordinating production, procurement and inventory schedules, conducting regular departmental meetings, improving information sharing, and reducing operational errors enhance organizational efficiency. Pearson correlation analysis showed a strong positive and statistically significant relationship between internal integration and operational efficiency (r = 0.813, p < 0.001). Regression analysis indicated that internal integration significantly predicted operational efficiency, explaining 77.4% of its variation (R² = 0.774). The study concluded that effective internal integration improves coordination, resource utilization, decision-making, and operational performance at Sulfo Rwanda Industries. The study recommends strengthening interdepartmental coordination, investing in integrated information systems, promoting collaborative planning, and improving communication mechanisms to enhance operational efficiency and competitiveness among distribution firms in Rwanda.