The majority of internet users today find their news on social media (Gil de Zúñiga et al., 2017), however, media trust, and especially trust in social media is low. (Edelman, 2019) In growing political polarization the effects of perceived media hostility are also gaining more importance. In this research readers of international news were surveyed in an online experiment to assess how issue involvement on the 2020 military conflict between the United States and Iran correlates with general trust in the media and with the credibility of the largest social media network, Facebook, as a news source. The current research investigated whether the hostile media effect still occurs in a purely social media context and results showed that partisans (those with a strong supporting or opposing opinion on the military conflict) perceive news content on Facebook as hostile along the same lines as they do in a traditional media context. This study also made an attempt to understand how content creation is related to bias perception, namely, what segments of social news content and which mainstream journalistic role contribute to perceived bias. This study fills the literature gap of the hostile media effect in a social media context. Findings may also have implications for the news industry as to how journalist roles and content segments influence audience perceptions.