Latar Belakang: Imunisasi merupakan salah satu upaya penting untuk mencegah penyakit menular pada bayi, namun kecemasan ibu terhadap efek samping imunisasi, seperti demam, rewel, dan bengkak pada tempat suntikan, dapat memengaruhi kepatuhan terhadap imunisasi. Pengetahuan ibu mengenai imunisasi menjadi faktor penting dalam menurunkan kecemasan tersebut. Tujuan: Penelitian ini bertujuan untuk mengetahui hubungan antara pengetahuan ibu tentang imunisasi Pentabio (DPT-HB-Hib) dan Pneumococcal Conjugate Vaccine (PCV) dengan tingkat kecemasan ibu terhadap efek samping pemberian imunisasi di TPMB “NKN”. Metode: Desain penelitian menggunakan pendekatan kuantitatif dengan desain cross-sectional. Sampel penelitian terdiri dari 134 ibu yang memiliki bayi usia 2-12 bulan yang dipilih menggunakan teknik accidental sampling. Data dikumpulkan melalui kuesioner pengetahuan dan tingkat kecemasan menggunakan Hamilton Rating Scale for Anxiety (HARS-A). Analisis data menggunakan uji korelasi Spearman. Hasil: Hasil penelitian menunjukkan mayoritas responden memiliki pengetahuan cukup (65,7%) dan tingkat kecemasan ringan hingga sedang. Terdapat hubungan signifikan antara pengetahuan ibu tentang imunisasi Pentabio dan PCV dengan tingkat kecemasan ibu terhadap efek samping imunisasi (p-value

Background: Immunization is a key effort in preventing infectious diseases in infants. However, maternal anxiety about post-immunization side effects such as fever, fussiness, and swelling at the injection site can influence compliance with immunization schedules. A mother's knowledge of immunization plays an important role in reducing this anxiety. Purpose: To determine the correlation between mothers’ knowledge of Pentabio (DPT-HB-Hib) and Pneumococcal Conjugate Vaccine (PCV) immunizations and anxiety of mother levels toward the side effects of immunization at TPMB "NKN." Method: This study employed a quantitative approach with a cross-sectional design. There were 134 mothers and infants aged 2–12 months recruited as a sample for the study, which was selected using accidental sampling. Data were collected using a knowledge questionnaire and the Hamilton Rating Scale for Anxiety (HARS-A). Data were analyzed using the Spearman correlation test. Result: The findings showed that the majority of the respondents had moderate knowledge (65.7%) and experienced mild to moderate anxiety. A significant correlation was found between mothers’ knowledge of Pentabio and PCV immunizations and anxiety of mother levels about immunization side effects (p-value < 0.001), with a moderate negative correlation: the higher the knowledge, the lower the anxiety. Conclusion: Healthcare practitioners are suggested to deliver more thorough education regarding the advantages, schedules, and management of immunization side effects to reduce maternal anxiety. Keywords: Knowledge, Anxiety, Immunization