As innovative digital technologies have become a key competitive weapon in the logistics service industry. Such circumstance has enforced logistics service providers (LSPs) to transform themselves into digital to maintain their competitive advantage. It is therefore essential for LSPs to understand the critical success factors (CSFs) in digital transformation (DT). This study attempts to investigate the causal relationships among CSFs. The logistics service industry in Thailand is used as a case study. Through extensive literature review, nineteen CSFs are identified. The questionnaire is developed to gather data from five qualified industrial experts. Grey DEMATEL approach is deployed to analyze the causal relationship among CSFs and categorize them into cause or effect groups. The finding from this study can help the scholars and practitioners in the field of logistics service to better understand the CSFs of DT and their interrelationships.