Complete Basic Immunization (CBI) or Imunisasi Dasar Lengkap (IDL) is an essential public health intervention for protecting children against vaccine-preventable diseases (VPDs). However, CBI coverage in Banda Aceh has declined over the past five years, decreasing from 37.8% in 2023 to 34.9% in 2024, including at Lampaseh Community Health Center. This study aimed to examine the association between predisposing factors (knowledge and attitude) and enabling factors (family support and availability of immunization services) with parents’ readiness to complete basic immunization at Lampaseh Community Health Center, Banda Aceh. A quantitative cross-sectional study involved 55 parents of infants aged 0–24 months selected using purposive sampling. Data were collected through structured questionnaires and analyzed using univariate analysis, Chi-Square test for bivariate analysis, and multiple logistic regression for multivariate analysis. The results showed significant associations between knowledge (p = 0.001), attitude (p = 0.020), and family support (p = 0.003) with parents’ readiness to complete basic immunization. Conversely, availability of immunization services was not significantly associated with readiness (p = 0.465). Multivariate analysis identified knowledge as the most dominant factor associated with readiness (p = 0.032; OR = 6.601). Parents with good knowledge were 6.6 times more likely to be ready to complete their children’s basic immunization compared with those with inadequate knowledge. These findings highlight the importance of improving parental knowledge, strengthening positive attitudes, and increasing family support through effective health education and promotion programs to enhance immunization completion among children in Indonesia.