Although the relationships between some antecedents (such as affective disorders and negative emotions) and short-form video addiction have been verified by previous studies, the association between negative cognitive bias and this addictive behavior has not been examined, and the underlying psychological mechanisms are still unclear. The present study explored the relationship between negative cognitive bias and short-form video addiction as well as the mediating roles of social support and loneliness in this association. The participants of the current study included 336 university students (197 females). The findings showed that (1) negative cognitive bias was positively correlated with short-form video addiction; (2) social support and loneliness separately mediated the relationship between negative cognitive bias and short-form video addiction; and (3) social support and loneliness sequentially mediated the relationship between negative cognitive bias and short-form video addiction. These results might be helpful for understanding the relationships and the underlying psychological mechanisms between these study variables. Future studies were encouraged to investigate effective intervention approaches for relieving negative cognitive bias, which might be conducive to decreasing the severity of short-form video addiction.