Risk factors for problematic smartphone use (PSU) have rapidly become an important area of research due to the prevalence of smartphones and functional impairment associated with PSU. Our aim was to examine relations between established predictors of PSU (depression and anxiety) and a potential mediator of PSU (anxiety sensitivity; AS). Participants (
N
= 4752) from junior and senior high schools in Tianjin, China completed a web‐based survey with measures of depression, anxiety, AS, and PSU. Descriptive and inferential analyses revealed significant differences between males and females on depression severity, and between junior and senior high school students on AS and PSU severity. Results of structural equation modeling indicated that anxiety was positively associated with AS when adjusting for depression; and AS was significantly associated with greater PSU severity, adjusting for age and sex. Additionally, AS mediated relations between anxiety and PSU severity. Current findings on AS are consistent with theoretical models of problematic internet use (Interaction of Person‐Affect‐Cognition‐Execution) and previous research linking AS to other kinds of behavioral addictions (e.g., smoking, alcohol use).