<p>Reliable measurement tools are essential for assessing facility performance and guiding digital tool implementation maturity. Despite Ethiopia’s progress in digital tool implementation and maturity, the lack of a standardized instrument to assess digital supply chain maturity remains a significant challenge. The lower-level pharmaceutical supply system (Dagu) is a locally developed open-source platform in the supply chain system designed to provide systematic record-keeping and manage health commodities in Ethiopia. This study aimed to develop and validate Dagu maturity assessment tool at primary healthcare units in Ethiopia. A cross-sectional study was conducted in all Dagu system implementing facilities in Ethiopia. Item identification, domain generation, and establishment of face and content validity were conducted. Data were collected electronically using the Open Data Kit and analyzed using R version 3.4.6. Factor analysis assumptions such as KMO and Bartlett’s test of Sphericity, were checked, and confirmatory factor analysis was carried out to determine item loading across measurement domains. Model fitness was assessed using Root Mean Square Error of Approximation (RMSEA), Comparative Fit Index (CFI), Tucker–Lewis Index (TLI) and Standardized Root Mean Square Residual (SRMR). Item-level explanatory power was evaluated using square multiple correlation (R²). A total of 365 facilities were included for psychometric development and validation. Dagu implementation maturity tool was developed, comprising five domains, twenty-four sub-domains and ninety-four stages of progression with a strong content validity index. The largest factor loading was found in issue data quality, while the lowest was found in stock according to plan. Similarly, the data quality domain demonstrates the highest reliability among the domains identified. The model fit indices were found to be acceptable: RMSEA = 0.079, SRMR = 0.062, TLI = 0.904, and CFI = 0.921. The highest R² was reported for issue completeness, followed by receive completeness while the lowest R² was found in stocked according to plan. This study provides the first validated tool to measure supply chain digital tool implementation maturity in Ethiopia’s primary healthcare. The tool reveals strong psychometric performance and highlights the importance of domains, sub-domains and stages of progression identified for supply chain digital tool maturity assessment. This tool can be applied in similar settings to track facilities digital tool maturity progress.</p>