The purposes of the current study are (1) to conceptualize and test a social networking service (SNS) dependency measure and (2) to propose and test a general model of the effect of SNS dependency on online and offline interpersonal storytelling. This study is theoretically guided by media system dependency theory and communication infrastructure theory. Computer-assisted personal interviews (CAPI) were conducted with 477 SNS users aged 19–59 in Seoul in October of 2012. Confirmatory factor analyses results showed that our SNS dependency measure was valid and reliable. The results also confirmed that SNS dependency had direct effects on individual users’ levels of engagement with interactive activities on SNSs and indirect effects on offline interpersonal storytelling.