Based on the six key components of addiction, the Bergen Facebook Addiction Scale (BFAS) is a widely used instrument to assess Facebook addiction. This study aimed to conduct a psychometric validation in a Portuguese sample of emerging adults (ages 18 to 29 years). The construct validity analyses confirmed the one-factor solution and a statistically significant association found between Facebook addiction and Preference for Online Social Interaction, measured by the Generalized Problematic Internet Use Scale 2, warranted the scale criterion validity. Internal consistency was scrutinized using Cronbach's α (α = .87) and stability measured by test-retest (r = .94). Associations between BFAS scores and Brief Symptom Inventory dimensions scores (e.g., interpersonal sensitivity, depression, anxiety) and the GPIUS2 subscale, deficient self-regulation, scores were evaluated. A subsample with higher levels of addiction was analyzed. In summary, the results of the present study support the use of the Portuguese version of the BFAS in both research and clinical milieus. Further implications for research and practice were considered. Keywords Behavioral addiction. Social networking sites. Bergen Facebook addiction scale (BFAS). Portuguese psychometric studies. Emerging adults Social networking sites (SNSs) are a global phenomenon, enjoying an exponential increase in their use (e.g., Facebook, Twitter). Participation in SNSs is currently one of the main activities on the Internet, especially for younger generations (Eurostat 2016; Kuss and Griffiths 2011). In Portugal, the use of SNSs is also extremely popular, being one of the preferred online activities of Portuguese adolescents and young adults (Pontes and Patrão 2014). SNSs constitute virtual communities where users can: (1) create a public or semi-public profile, (2) manage a list of other users with whom they have a connection, and (3) view and intersect their list of connections with those made by other users (Boyd and Ellison 2008). One specific aspect of SNSs is their focus on