It is known that breastfeeding difficulties are often seen in the first weeks of the postpartum period and that various factors are effective in the mother's early cessation of breastfeeding. Mothers' self-efficacy and perception of insufficient milk are among these factors. This study aimed to examine the effect of hot application applied to the breast with the help of Thera Pearl in the postpartum period on milk perception and postpartum breastfeeding self-efficacy. This is a randomized controlled study. The study was completed with a total of 64 puerperal mothers, 31 of whom were control and 33 were experimental. Personal Information Form, Breastfeeding Observation Form, Breastfeeding Self-Efficacy Scale and Insufficient Milk Perception Scale were used to collect data. As a result, self-efficacy and milk perception are important factors affecting breastfeeding. In this study, we found that Thera pearl application increased breastfeeding self-efficacy, but did not affect milk perception.