Sound and reliable information is the foundation of decision-making across all health system building blocks and is essential for health system policy development and its implementation. Ethiopian health sector transformation plan has given special attention to health information management, data use intending to promote the quality and culture of health information data use for decision making. Hence, this study aims to assess the practice of routine Health Information data use for decision-making and its determinants in Fafan Zone Somali region.A cross-sectional study was carried out in August 2021 to assess routine Health Information, data use practices, and its determinants in the Fafan zone Somali region. The participants of the study were 359 health workers from different departments of selected health centers and woreda health offices by using cluster-sampling techniques. The study findings showed that the health workers' practice of RHI data use for decision-making is very low. The determinants of Routine health information management data use practice that was identified in the study include work position level, Health worker's educational level, presence of regular Supportive supervision flowed by timely feedback on performance, training status of data users, and availability of all required inputs for the preparation and display information, and data management guidelines. Therefore, enhancing knowledge, skills, data management inputs, supportive monitoring, and access to user training are important to expand the use of routine health information data in health centers and woreda health offices in the Fafan zone.