On August 14, 2017, a 6-kilometer mudslide occurred in Regent Area, Western Area District of Sierra Leone following a torrential downpour that lasted 3 days. More than 300 houses along River Juba were submerged; 1141 people were reported dead or missing and 5905 displaced. In response to the mudslide, the World Health Organization (WHO) Country Office in Sierra Leone moved swiftly to verify the emergency and constitute an incident management team to coordinate the response. Early contact was made with the Ministry of Health and Sanitation and health sector partners. A Public Health Emergency Operations Center was set up to coordinate the response. Joint assessments, planning, and response among health sector partners ensured effectiveness and efficiency. Oral cholera vaccination was administered to high-risk populations to prevent a cholera outbreak. Surveillance for 4 waterborne diseases was enhanced through daily reporting from 9 health facilities serving the affected population. Performance standards from the WHO Emergency Response Framework were used to monitor the emergency response. An assessment of the country’s performance showed that the country’s response was well executed. To improve future response, we recommend enhanced district level preparedness, update of disaster response protocols, and pre-disaster mapping of health sector partners.