The mechanisms underlying how and when harsh parenting increases the risk of smartphone addiction are far from being understood. Meanwhile, studies examining protective factors against the effects of harsh parenting on smartphone addiction are still scarce. In this study, a moderated mediation model was constructed to investigate the potential mechanisms behind the effect of harsh parenting on smartphone addiction, and highlight the possible protective role of core self-evaluation as a mediating variable and nature connectedness as a moderating variable in this relationship. The sample consisted of 1316 college students ranging in age between 18 and 23 years old (M = 18.96, SD = 1.54 years, 77.05% female) from two universities located in Central China. Participants completed questionnaires regarding demographics, harsh parenting, smartphone addiction, core self-evaluations, and connectedness to nature. Hayes PROCESS macro for SPSS was used to test the hypothesized model. After demographic covariates were controlled for, the results revealed that: (a) harsh parenting was positively associated with smartphone addiction; (b) core self-evaluations mediated the relationship between harsh parenting and smartphone addiction; and (c) nature connectedness could moderate the effect of harsh parenting on core self-evaluations. The findings of this work may help guide interventions to prevent smartphone addiction among college students. Implications for practice was discussed.