<p>With the growing number of social media users, the prevalence of flaming is making computer-mediated communication (CMC) increasingly aggressive. Previous studies have demonstrated that cyberostracism is an important risk factor for flaming. However, the underlying mechanism remains unclear. Based on the general aggression model and temporal need-threat model, the present study assumed that the numb state experienced by ostracized individuals may play a crucial role in this relationship. Following dehumanization theory, the present study proposes that cyberostracism induces a numb state (i.e., self-dehumanization), which in turn reduces empathy, ultimately leading to flaming. Thus, the present study measured cyberostracism, flaming, self-dehumanization, and empathy. Structural equation modeling was employed to examine the chained mediation model linking cyberostracism to flaming. The results confirmed that cyberostracism positively predicted flaming, with self-dehumanization serving as a mediating factor in this relationship. Since empathy did not significantly predict flaming, self-dehumanization and empathy did not play a chained mediating role in the cyberostracism-flaming link, as initially hypothesized. The findings uncovered the underlying mechanism of the cyberostracism-flaming link, extending self-dehumanization theory in CMC. Additionally, it offers practical insights into reducing flaming by promoting netizens’ sense of humanity.</p>