Immunization pain is a stimulus that can cause trauma and changes affective response in the baby. Breastfeeding is one of the strategies to reduce pain response due to minor invasive procedures. This study was aimed to determine the effect of breastfeeding on infant pain levels when getting pentavalent immunization. This research was used Randomized Controlled Trial with unblind design unblind, post-test design, with a sample of 70 healthy infants consisted of 34 respondents intervention group and 36 respondents of the control group were selected by random block technique. this study that showed the pain level of intervention group is lower than the level of pain group (p = 0.000; α = 0.05). breast-fed infants when immunized can reduce the risk of severe pain by 80% compared to infants who are not breastfed. Further research on the effect of breastfeeding for preterm infants pain response in invasive procedure.