Strengthening routine immunization is one of the four prongs of the Global Polio Eradication Initiative. Achieving this requires improving immunization coverage in hard-to-reach areas. The objectives of this analysis were to assess levels of oral polio vaccination coverage and challenges in pastoral and semi-pastoral regions in Ethiopia. The analysis included vaccination-related data for children aged 12-23 months from the 2011 Ethiopian Demographic and Health Survey (EDHS) and from surveys carried out by the CORE Group Polio Project (CGPP) in 2013, 2015, and 2017. The EDHS data were from the entire regions (states) of Somali; Oromia; Southern Nations, Nationalities, and Peoples; Benshangul-Gumuz; and Gambella, whereas the CGPP data were for portions of these states where the CGPP was working and consisted entirely of pastoralist or semi-pastoralist populations. The overall polio immunization coverage rate showed upward trend from 39.6% in the 2011 EDHS to 72.6% for 2017 survey of children in the CGPP intervention areas. The evidence suggests that the CGPP was able to achieve increasing levels of coverage in the hardest-to-reach areas of these states and that the levels were higher than those achieved in the states as a whole. The strategies used by the CGPP/Ethiopia to increase coverage appear to have been effective. Other characteristics associated with full polio immunization included mother's religion and education, whether the mother had heard about polio, knowledge on the effect of many polio vaccine doses, and age at first polio immunization.