Despite expansive scale-up of prevention of mother-to-child transmission (PMTCT) of HIV services in Kenya over the last decade, Kenya remains one of the countries contributing high numbers of children living with HIV globally and among the 22 PMTCT global plan priority countries. Using a mixed methods approach this study examined enabling factors –individual, social and structural – that enhance utilization of and adherence to PMTCT services in a plural urban setting in Kenya. The study was conducted from October-December of 2012 at St. Mary’s Mission Hospital, Lang’ata. HIV-positive birthmothers whose infants were HIV-negative at the time of the study were purposively selected to participate. All informants completed an interviewer-administered questionnaire (n = 55) and a subset (n = 15) participated in in-depth interviews. Contrary to the assertions of multiple studies that failures of PMTCT programs are a result of inadequate knowledge of mother-to-child transmission and PMTCT interventions, lack of support and acceptance by family and community, as well as poor quality of services, this study found these factors to be statistically insignificant in explaining PMTCT achievements. The study further found that HIV/AIDS related stigma and gender imbalances create many missed opportunities for HIV-positive mothers to apply acquired knowledge on mother-to-child transmission and PMTCT interventions, mobilize support from family and community, and access more affordable care. Factors found to influence women’s decisions to utilize and adhere to PMTCT services include supportive counseling, striving for motherhood, maternal attachment and concern for the child’s wellbeing, assurance of confidentiality and testimonials of other successful mothers. Based on the study findings, policy recommendations have been proposed along with suggestions for future research.