Our purpose in this web-based study was to relate smartphone and nonsmartphone use to symptoms of mobile phone dependency, and to examine sociability in this context. We used a stratified sampling method to recruit 551 Singaporean undergraduates. The results showed that young smartphone users tended to have greater mobile phone dependency and more severe symptoms than nonsmartphone users did. We found that utilizing mobile Internet and text messaging were both positively associated with smartphone users’ dependency. Regardless of phone type used, the level of sociability of mobile phone users was positively associated with mobile dependency and symptoms of feeling anxious and lost, and withdrawal/escape.