This evaluation was commissioned with the objective to enhance future operational performance by means of lessons learned from the intervention in Hajjah Governorate from 30 March to October 2017 in order to reduce morbidity and mortality caused by cholera outbreaks in similarly complex settings. Evaluation findings showed that the intervention contributed to reduce morbidity, mortality and human suffering, even though data collection was chaotic in the beginning. The impact of this response can be attributed to the dedication and engagement of MSF staff, both Yemeni and international, who demonstrated a great deal of energy to the cholera response despite their limited experience in dealing with the disease. The main challenges were lack of preparedness and cholera expertise in the mission. This was aggravated by delays of having additional technical staff (difficulties to get visas). The frequent absence and high expatriate turnover in key positions created significant hindrances, which affected many programme components in CTC/CTU as well as outreach activities.