While social media’s positivity bias has been linked to various well-being implications, little is known about how it relates to young adults’ romantic cognitions and outcomes. This study explores the associations between perceived exposure to positively-biased romantic social media content and relationship satisfaction, as well as fear of being single (FOBS). A cross-sectional survey (N = 605) was administered and a separate model was tested for young adults in a committed relationship for the outcome relationship satisfaction and for single young adults for the outcome FOBS, by using Structural Equation Modeling. Both models considered romantic partner expectations as a mediator and tested gender and social comparison orientation (SCO) as moderators. Perceived exposure to positively-biased portrayals was negatively associated with relationship satisfaction. There was no link with FOBS. For young adults in a committed relationship, higher partner expectations related positively to relationship satisfaction but were not predicted by exposure to positively-biased portrayals. For singles, exposure to such content did predict higher partner expectations but this did not, in turn, relate to FOBS. Also no significant moderation effects were found for gender and SCO. Our findings highlight the nuanced ways in which the positivity bias can relate to romantic outcomes and underscore the value of authenticity on social media.