Synchronized polio supplementary immunization activities (SIAs) were conducted in Ethiopia, Somalia, and Djibouti on 14–18 June 2014 to accelerate progress towards ending polio in the Horn of Africa. The synchronized SIAs were an outcome of the Horn of Africa Countries Synchronized Cross-Border Polio Outbreak Preparedness and Response Meeting in Jijgiga, 21–23 May 2014, where Ethiopia, Somalia, Kenya and Djibouti agreed to strengthen cross-border collaboration to kick polio out of the Horn of Africa.