Social media addiction refers to the frequent and compulsive use of social media sites that interferes with important areas of functioning. There is a growing body of research showing that social media addiction is related to sexual difficulties, which might result, at least partly, from sexual function impairment secondary to adverse effects of social media misuse on psychological well-being and intimate relationship quality. However, the investigation into this topic is still scarce. The present study examines if social media addiction is inversely correlated with sexual satisfaction, and if this association is mediated by relationship satisfaction and mental health satisfaction. Stratified quota sampling was used to recruit a sample of 3,594 Portuguese who used social media and were involved in a romantic relationship (age range: 18 – 69). Participants completed the Internet Addiction Test adapted to social media and single-items measuring satisfaction with sex life, relationship, and mental health. For women and men, greater social media addiction correlated inversely with sexual satisfaction. This association was mediated by relationship satisfaction and mental health satisfaction in parallel multiple mediation tests. The findings confirm that misuse of social media is associated with sexual problems. This might be due to 1) social media addiction interfering with relationship quality, 2) social media causing mental health disturbances that impact sexual function, 3) greater vulnerability to social media addiction being increased by relationship and/or mental health problems that also interfere with sexual satisfaction. The findings are important for raising awareness of potential risks of social media misuse.