Previous research has detailed concerns that exposure to both pro- and counter- attitudinal content on social media can result in outcomes of ideological polarization (e.g. Bail et al., 2018; Lu & Lee, 2018). However, further research is needed in order to understand the conditions under which this polarization may take place. To investigate this issue, this study utilizes a sample of 414 social media users in the U.S. to investigate the mediating effects of a) anger toward political opposites and b) anger toward oppositional social media content on the relationships between various types of political content exposure and the outcome of ideological polarization. Results revealed that both types of politically oriented anger partially or fully mediated all relationships between the explanatory variables and the outcome variable, demonstrating that exposure to all types of political content on social media can affect polarization through the mechanism of anger. Theoretical implications for the echo chamber theory and the backfire effect are discussed.