Infantile colic has a multifactorial etiology. Recent studies have suggested that probiotics may be effective in its management. This study was carried out to evaluate the effect of the Actiregularis strain (5×106 cfu\ml) included in maternal nutrition on gastrointestinal problems, growth development, and breastfeeding outcomes in infantile colic. The study was a randomized controlled trial conducted in the neonatal outpatient clinic of a training and research hospital in Turkey. A probiotic drink containing the Actiregularis (5×106 cfu\ml) strain was added to the diet of mothers in the probiotics group once daily for 15 consecutive days. Data were collected for each infant's 0th (birth), 1st, 4th, and 6th months. Infants whose mothers were administered Actiregularis for 15 days had decreased crying intensity (P = 0.000). When the difference in breastfeeding rates between the groups was significant at the 4th and 6th months (P = 0.044; P = 0.035). There was no difference in anthropometric values except the babies' weights at the 6th month. (P < 0.001). Infants treated with Actiregularis, which was added to their mothers' diet for 15 days, showed a decrease in the frequency of crying, and the difference in breastfeeding rates between the groups was significant at the 4th and 6th months. There was no difference in anthropometric values except the babies' weights at the 6th month. NCT04374955 (https://clinicaltrials.gov/ct2/show/).