Background: Although WhatsApp can be used to provide continuous lactation support, there are few studies on this subject. Research Aims: To determine the influence of lactation support provided through WhatsApp on the duration and exclusivity of breastfeeding, initiation of complementary feeding, breastfeeding problems, breastfeeding difficulties score, and the use of bottles and pacifiers. Methods: We conducted a randomized controlled trial assessing the efficacy of education and support provided through the cell phone based WhatsApp application. There were 129 primiparous participants recruited while attending a Baby-Friendly Hospital in Istanbul, Turkey. Participants were randomized to intervention ( n = 64) and control ( n = 65) groups. All participants received the same routine postpartum breastfeeding education in the hospital, and the intervention group received additional continuous breastfeeding education for 6 months. For both groups, data was collected by telephone interview on Days 7 and 15, and Months 1, 2, 4, and 6 months. T-tests were used to assess inter-group differences in duration of exclusivity of breastfeeding. Mixed-model ANOVA was used to compare breastfeeding difficulties scores. Chi-square tests were used to compare breastfeeding problems, feeding practices, and the proportion of the use of bottles and pacifiers. Results: The mean duration of exclusive breastfeeding for groups receiving breastfeeding support was higher (4.75, SD = 1.72) than that of the control group (2.21, SD = 1.98; p = 0.001). The change in the mean breastfeeding difficulties severity score between the initial and final measurements (17.03, SD = 8.66) was more in the intervention group than the control group (11.42, SD = 10.34, F = 4.081, p = 0.001). The proportion of exclusive breastfeeding in the 6th month was higher in the intervention group (62.5%) than in the control group (10.8%; p = 0.001). Conclusions: The use of cellphone applications are accessible to both patients and health workers and offer a low-cost alternative for providing uninterrupted breastfeeding support.