Scholars have recently taken an interest in the connection between narcissism and Internet use, especially among users who frequent social networking sites (SNSs). Conversely, the association between narcissism and problematic use of SNSs (i.e., unregulated use that leads to negative outcomes) has been scarcely investigated. This study addresses this gap by comparing the mean levels of problematic use of SNSs among grandiose narcissists, vulnerable narcissists, and non-narcissists. A sample of 535 students completed the 16-item Narcissistic Personality Inventory, the Hypersensitive Narcissism Scale, and the Generalized Problematic Internet Use Scale-2 (GPIUS2). Vulnerable narcissists reported (a) significant higher levels on all GPIUS2 subscales and total scores than non-narcissists and (b) a stronger preference for online social interactions and higher overall levels of problematic use of SNSs than grandiose narcissists. Conversely, no significant differences were found between grandiose narcissists and non-narcissists. This study suggests that vulnerable narcissism may contribute more to problematic use of SNSs than grandiose narcissism.