The main objective of this study was to examine determinants of infant immunization coverage in Migori County; Nyanza. Migori-Nyanza is the regions of disparities that continue to register low rates of immunization coverage in Kenya. The coverage rate was measured against Kenya's and World Health Organization target percent for achieving herd immunity and improved child survival. Immunization coverage rates are accepted as an indicator of the performance and adequacy of a Country's Health Service Systems. A descriptive study of 446 households sampling units was conducted in January 2013. The households were randomly selected from four demand areas. Methods of data collection were: interviewer administered questionnaires, key informant interviews and homogeneous focus group discussions. Respondents were mothers aged 19-45 years with a child less than five years of age. The results indicated that fully immunized infants were 70%; a fully immunized infant was one who received one dose of BCG, four doses of Oral Polio Vaccine (OPV), three pentavalents, and one dose of measles vaccine before reaching one year of age. The results further indicated that:-80% of infants had their birth polio and Bacillus-Calmette Guerin (BCG) within the first two weeks of life, 78% 3 rd pentavalent and 4 th polio at 14 weeks of life and 77% measles at 9 months. Measles and third dose of pentavalent immunizations are used as indicators of a fully immunized child. The determinants of immunization coverage that were identified from the study included: means of transport to health facilities, religious affiliation, home delivery and not attending postnatal clinics, mothers' lack of knowledge on dangers of childhood diseases and hostile attitudes shown by service providers to the mothers. In conclusion there was under coverage of immunization in the region. The recommendation was that the health service providers need to in-cooperate both outreach and mobile immunization services into their current static module.