With ongoing research, increased information sharing and knowledge exchange, humanitarian organizations have an increasing amount of evidence at their disposal to support their decisions. Nevertheless, effectively building decisions on the increasing amount of insights and information remains challenging. At the individual, organizational, and environmental levels, various factors influence the use of evidence in the decision-making process. This research examined these factors and specifically their influence in a case-study on humanitarian organizations and their WASH interventions in Uganda. Interviewees reported several factors that impede the implementation of evidence-based decision making. Revealing that, despite advancements in the past years, evidence-based information itself is relatively small, contradictory, and non-repeatable. Moreover, the information is often not connected or in a format that can be acted upon. Most importantly, however, are the human aspects and organizational settings that limit access to and use of supporting data, information, and evidence. This research shows the importance of considering these factors, in addition to invest in creating knowledge and technologies to support evidence-based decision-making.