As projections of climate change effects in the media persist, current research suggests that threatening climate change content circulating social media and knowledge of threats to the Earth system and human health may lead to the development of eco-anxiety. If social media exposure to climate change content influences eco-anxiety, there is a need for psychological interventions to help manage climate change-related negative affect. A systematic review was conducted 1) to investigate the relationship between the use of social media and eco-anxiety in young adults and 2) to explore methodological factors involved in eco-anxiety research, including measurements and potential moderating factors. The review included seventeen articles that studied the measurements of eco-anxiety, the relationship between social media and eco-anxiety, or negative affect related to climate change and potentially moderating risk factors. A thematic analysis of the included articles yielded four central themes: (1) The Operationalization of Eco-anxiety, (2) Climate Change Perceptions and their Effects on Impairments, (3) The Relationship between Social Media Usage and Eco-anxiety, and (4) Potential Factors Influencing Climate Change Perceptions. The results suggest that eco-anxiety is real and common, especially amongst young people, and that it may be reliably measured using the Climate Change Anxiety Scale. Due to the limited and heterogeneous literature on the problem, no definitive conclusions can be drawn about how potential factors influence eco-anxiety. Future research should further explore the relationship between social media and eco-anxiety. In addition, the problem of eco-anxiety should be studied in underrepresented, vulnerable populations at higher risk for weather-related events.