The purpose of this study was to determine the effect of smartphone use on the social personal development of children in school at Al-Marhamah Kindergarten. This study used quantitative methods with cross sectional design. The population in this study were all parents of students and Al-Marhamah kindergarten students in Majalengka Regency with  total sample of 33 mothers  and 33 children. Tthe sampling technique used was simple random sampling. The analysis used univariate by using frequency distribution and bivariate by using Chi Square test with α = (0, 05). The results showed that there was an influence between the use of mobile phones and social personal development of pre-school age children with the probability value p 0.017 <0.05 (Ho was rejected because the value <0.05). Suggestions are proposed for teachers as parents in kindergarten to emphasize that the use of smartphone at home needs to be supervised by parents so that children can wisely use it with  appropriate duration to children age, meanwhile,  parents can play an active role in supervising smartphone use as well as in the process of maturity child development. Keywords: smartphone, social development, pre-school age children