This chapter presents an overview of how observers detect ostracism, how they interpret and evaluate it, and how they react to it. It suggests how to create an intervention that raises observers’ awareness of ostracism and helps them to make more informed moral judgments that are less prone to potential bias. The reasons for ostracism differ, and just as ostracism situations can be perceived and processed differently by the targets of ostracism, observers’ reactions may differ as well. Ostracism is very painful and threatening for targets, but it has repeatedly been shown that social support can buffer the negative impact that ostracism inflicts on an individual’s well-being. Observers can attribute ostracism to a malicious motive of the ostracizing group, such as ingroup favoritism, racism, selfishness, or lust for power. Attributing ostracism is relatively easy when observers either know about the sources’ motives or have witnessed the events that resulted in ostracism of the target.