Previous research has shown that ostracism—the experience of being ignored and excluded—has negative effects on all of us, young and old. Using a Cyberball paradigm, the present research replicates the effects of ostracism on the moods (anger, anxiety, happiness, and anger) and fundamental needs (belongingness, control, meaningful existence, and self‐esteem) of children (Study 1) and then extends the literature by examining the role of the number of ostracizers and inclusive members in this process by randomly assigning children to conditions varying in degree of ostracism (Study 2). Results of both studies showed that experiencing ostracism strongly and negatively affected all moods and fundamental needs—with the exception of anxiety. Study 2 in addition showed that the ratio of excluders to inclusive group members had different effects across outcomes. In all cases, complete ostracism produced the worst outcomes, suggesting that the presence of even a single ally reduces children's distress. For sadness, unanimous ostracism seemed particularly toxic. In some cases, facing two ostracizers produced significantly worse outcomes than only one, suggesting that consensual rejection might drive the negative effects on happiness, and sense of belonging, control, and meaningful existence. For self‐esteem, only one ostracizer (in the presence of two inclusive members) was sufficient to induce a negative effect. Aggr. Behav. 43:190–203, 2017. © 2016 Wiley Periodicals, Inc.