More than one fourth of children of HIV-infected mothers living in Kolkata city are not completely immunized by 12 months of age. This qualitative study aims to explore the barriers to immunization of these children as perceived by their caregivers and the local health care service providers. In-depth interviews were conducted after obtaining written informed consent. Audio recording and hand-recorded notes were used with permission. The transcripts were coded and analyzed using grounded theory. Deteriorating socioeconomic status, tightening of time schedule of caregivers due to illness in the family, stigma, discrimination, and lack of awareness about immunization prove to be major barriers for immunization of the HIV-exposed children. Interplay of these factors coupled with harassment and negative attitudes of service providers toward HIV-affected/HIV-infected people also impede immunization. The intervention efforts need to address these social barriers and adverse life events to improve immunization coverage.