PURPOSE: The purpose of this study was to analyze the effects of academic stress among middle school students to their smartphone addiction while exploring the moderating effect of self-esteem and self-control in the relationship between academic stress and smartphone addiction. METHODS: A descriptive research design was used. The participants were 398 middle school students from one middle school in Seoul. A self-administered questionnaire was used to measure academic stress, self-esteem, self-control, and smartphone addiction. Data were analyzed with the SPSS/WIN 21.0 program. RESULTS: Smartphone addiction significantly differed according to gender, duration of smartphone use and average monthly amount of use. The hierarchical regression analyses revealed significant positive relations between academic stress and smartphone addiction. On the other hand, self-esteem and self-control were negatively related to smartphone addiction. Self-control appeared to have moderating effects in the relationship between academic stress and smartphone addiction. CONCLUSION: It is important when developing smartphone addiction prevention programs to consider self-control that showed moderating effects.