Immunization is the government's efforts to reduce children mortality, because immunization is an effective primary prevention to reduce infectious diseases. But the sufficient immunization number is still far to achieve the targets specified. There are many factors influence such as parents and families. The purpose of this study was to analyze the connection of the mothers’ knowledge with family roles (nuclear family and non-core family) alongside of basic immunization status. This research was an observational analytic study using cross sectional design. The sampling used cluster random sampling. Sampling in this research were 46 mothers of infants aged 9-12 month in community health center of  Pucuk Lamongan. Analysis of the data used was the chi-square test with significance level α of 0.05. The results showed a connection between mothers’ knowledge (p = 0.027), the role of the nuclear family (p = 0.007), and the role of non-core family (p = 0.020) with basic  immunization status. There is no connection between family’s income with basic  immunization status. (p = 0.725). The  conclusions  of the results this study of the mother's knowledge, the role of the nuclear family and non-core family has an important part to increase basic immunization coverage . As to develop KIE complete for mothers about basic immunization which should be obtained for infant. Motivate parents and family to always apply completeness of  basic  immunization, and  utilize the health care that has been provided to maintain the health of her infant.   Keywords: basic immunization, role of family, nuclear-noncore