Smartphone dependency (SD) has been linked to decreased happiness; however, research has not yet explored potential mediating mechanisms such as social class awareness (SCA) in this relationship. This study examined the association between SD and happiness among middle school students and the mediating effect of SCA in this relationship. Data from the 11th Korea-Child Happiness Index 2019 Survey were used, which is a cross-sectional survey administered to children and adolescents residing in South Korea collected by the Korea Social Science Data Archive (KOSSDA). A total of 2,296 Korean middle school students were selected for analysis. Findings suggest that higher levels of SD were associated with lower levels of happiness. SCA mediated the relationship between SD and happiness among middle school students. SD prevention and intervention approaches should consider the extent to which SCA impacts happiness of middle school students.