Using a quasi-experimental design, this study was conducted in two maternal & child health centres in Jordan to examine the effects of breast-feeding on pain relief during neonatal immunization injections. Inclusion criteria were first year of age, breast-fed and no concurrent illness. Infants were divided into two groups (of 60 infants for each). One is intervention group: mothers were taken to a private room, seated and reclined on a comfortable chair with their infants awake in their arms, without cloth and with clean diapers. The mothers cradled their infants during breast-feeding to maintain full-body skin-to-skin contact during immunization injections. The other is control group: infants were observed during routine immunization in maternal & child health centres. Pain responses of infants during and after immunization were assessed by using Facial Pain Rating Scale and Neonatal/Infant Pain Scale (NIPS), before, during and after the procedure. Infants' heart rates and duration of crying for both groups were calculated. Findings revealed that the crying time was shorter in intervention (breast-fed) group than in the control group with a statistically significant difference in the duration of crying during and after immunization. We concluded that, breast-feeding and skin-to-skin contact significantly reduced crying in infants receiving immunization.