A systematic review of the literature was conducted to summarize research that examined the associations between problematic social networking sites use (PSNSU) and attachment-related phenomena among adolescents and adults. Records were included in the systematic review if they presented original data, assessed attachment and PSNSU, were published in peer-reviewed journals between 2004 and 2021 and were written in English. After duplicates removal, 373 studies were found eligible for scrutiny. Among the screened full texts, 32 articles met the eligibility criteria. The selected studies included a total of 16,938 participants. Findings from these studies highlighted that PSNSU is negatively associated with indicators of secure attachment and positively associated with indicators of attachment anxiety, whereas results regarding indicators of attachment avoidance were mixed. Furthermore, an analysis of mediators showed that the relationship between PSNU and attachment-related phenomena is affected by individual, interpersonal, and SNS-related variables. Future directions for research as well as implications for clinical practice are discussed.