This study aims to evaluate the association between smartphone use and suicide attempts, independent of possible confounders, including conflicts with family/friends and poor academic performance due to smartphone use. Data were obtained from the 2017 Korea Youth Risk Behavior Web-based Survey, a nationally representative survey of middle- and high-school students (N = 62,276). Time spent using a smartphone was divided into four categories: less than 1 h, 1-2 h, 3-4 h, and 5 h or more a day. The association of conflicts with family due to smartphone use, conflicts with friends due to smartphone use, and poor academic performance due to smartphone use with suicide attempts and time spent using a smartphone were analyzed using multiple and binary logistic regression analyses, respectively. The relationship between time spent on a smartphone and suicide attempts was analyzed using a multiple logistic regression analysis. All analyses were also stratified according to the main purpose of smartphone use (process purposes/social purposes). Conflicts with family/friends due to smartphone use was significantly associated with suicide attempts (P <0.001). The variables of conflicts with family, conflicts with friends and poor academic performance were also proportionally related to higher smartphone use (P <0.001). The use of a smartphone was significantly associated with suicide attempts in a multiple logistic regression analysis (adjusted odds ratio for smartphone use 5 h or more a day 2.16; 95% CI 2.07-2.26; P <0.001), and the association was more prominent with smartphone use for process purposes. Conflicts with family, conflicts with friends, poor academic performance, and suicide attempts were related to higher smartphone use in Korean adolescents. Time spent on a smartphone was positively related to suicide attempts, even after adjusting for conflicts with family members or friends and poor academic performance due to smartphone use.