Tanzania introduced her Expanded Programme on Immunization (EPI), currently as known as Immunization and Vaccines Development (IVD) as project in 1975; this was one year after the 27th World Health Assembly (WHA), Agenda 57 resolution – WHA.27-57. To date, the country is having a strong national immunization programme which is delivering 7 types of vaccines combinations (namely BCG, OPV, Penta, TT, PCV-13, Rota vaccine and MR vaccines) as a major immunization programme service. This study aimed at assessing social factors that hinders accessibility of infants of un-married young women, to immunization programme services in Dar es salaam. The descriptive retrospective case control study design was deployed. A total of 214 young unmarried women aged less than 25 years were selected randomly, of which 196 were selected to participate in the study, this is 102% of the study sample size. Majority of these women were of age between 18 to 25 years (49.1%) and completed primary school (47.7%).In this study, social factors were observed to limiting the access of young unmarried women to immunization programme services. The common factors identified, were the older age group (p=0.015), mother’s education (p=0.293) and mothers occupation (p=0.487). Furthermore, it was perceived that, 66% of the mothers interviewed recalled 3 or more VPDs and mostly were given the immunization programme services information by health workers (67.3%, p=0.229), listening radio spots (47.7%, p=0.764) and some by reading posters (39.3%, p=0.157). The MOHGEC in collaboration with education sector stakeholders are urged to implement interventions to reduce teenage pregnancies; improve health information sharing among adolescents/young women; and streamlining of girls education policy and empowerment. Finally health workers should be trained on effective communication skills and screening of infant’s vaccination cards must be done regularly for infants seeking medical care.