This study aims to investigate the relationship between Facebook intensity and both the fear of missing out and smartphone addiction. It was carried out with 608 (437 female, 171 male) participating university students who were asked to complete the Facebook Intensity Scale, the Fear of Missing out Scale, and the Smart Phone Addiction Scale. The data were analyzed by Pearson correlation analysis and hierarchical regression analysis. The results of the correlation analyses indicated significant positive correlations between Facebook intensity and both fear of missing out and smartphone addiction. When categorical variables were taken into consideration, significant relationships were found between Facebook intensity and duration of Facebook use, age, and duration of internet use. Facebook intensity was significantly predicted by the duration Facebook use in the first block. In the second block, all variables explained 36% of the variance in the scores obtained from the Facebook Intensity Scale. In the second step, the most powerful predictor of Facebook intensity was duration of Facebook use, followed by the fear of missing out, and smartphone addiction. This study concluded that Facebook intensity could be predicted by the fear of missing out and smart phone addiction. It is suggested that this finding be taken into consideration for further research. Possible explanations of the findings and the implications and limitations of the study were discussed.