Ostracism is known to lead to negative psychological outcomes; however, little is known as to how ostracism may be a predictor of paranoid thoughts. The present paper examined the relationship between perceived ostracism and paranoid thoughts (social reference, persecution) by focusing on the potential moderating roles of psychological flexibility and inflexibility. As expected, data from a sample of 315 internet users (Mage = 31.5 years) showed that perceived ostracism was positively related to both social reference and persecution. Psychological flexibility did not moderate the ostracism-paranoid thought relationships. However, psychological inflexibility was a moderator of the ostracism-social reference relationship, but not for ostracism-persecution. Specifically, at both high and low levels of psychological inflexibility, there was a significant positive relationship between ostracism and social reference. These unexpected findings suggest that future research is needed to elucidate the mechanisms by which perceived ostracism may lead to paranoia.