<p>This study examined the impact of uncertainty on altruistic behavior in online contexts and explored its underlying mechanisms through three experiments involving college students. The findings revealed that: (1) uncertainty negatively affected college students’ Internet altruistic behaviors; (2) alienation acted as a mediator in the relationship between uncertainty and Internet altruistic behaviors; (3) group identity served as a moderating factor in the association between uncertainty and Internet altruistic behaviors. Specifically, high levels of group identity significantly mitigated the adverse effects of uncertainty on Internet altruistic behaviors, whereas this mitigating effect was comparatively weak among individuals with low levels of group identity. These findings contribute to our understanding of how uncertainty impacts Internet altruistic behavior and offer implications for interventions targeting college students’ online altruism.</p>