Objectives This study aims to test the mediating effects of social support on the relationship between parental psychological control, social support, interpersonal competency variables, and parental psychological control and interpersonal competence of college students. Methods To this end, 263 university students enrolled in universities in the metropolitan area were surveyed through questionnaires. The collected data were analyzed with SPSS 25.0 through descriptive statistics, Pearson correlation analysis, and hierarchical multiple regression analysis, and the significance of indirect effects was verified using the bootstrapping method. Results The main results are summarized as follows: First, after analyzing the correlation between each variable of parental psychological control, social support, and interpersonal competence, it was found that parental psychological control and interpersonal competence were significantly inadequately correlated, and parental psychological control and social support were also significant inadequacy correlations. Next, social support and interpersonal competence were significantly statically correlated. Second, parental psychological control affected interpersonal competence and had a negative effect on social support. Third, in the effect of parental psychological control on interpersonal competence, social support had a fully mediated effect. Conclusions Through the results of research that the higher the psychological control of parents, the lower the perception of social support, which negatively affects the development of interpersonal competence, we would like to provide basic data for the promotion of interpersonal competency in college students.