This study attempts to shed light on the structure, the prevalence and the determinants of anti-Walloon attitudes in Flanders. For this purpose, we contrast anti-Walloon prejudice with prejudice against a relatively well-understood and archetypical out-group, namely immigrants. Our theoretical approach draws on insights from two paradigms of intergroup relations: the Group-Focused Enmity approach stressing that specific prejudices have a strong common denominator, and the Differentiated Threat model arguing that specific prejudices are contingent on the context of intergroup relations as well as the involved types of threat. To assess the (dis)similarities in anti-Walloon and anti-immigrant prejudice, we use the Flemish dataset of the Belgian National Election Study (BNES) 2010. Comparable measurement instruments for both forms of prejudice are analyzed by means of structural equation modeling. Our results reveal a nuanced picture regarding the similarities and differences between anti-Walloon and anti-immigrant attitudes in Flanders. One the one hand, anti-Walloon and anti-immigration attitudes are strongly correlated and rooted in economic threat perceptions. On the other hand, anti-Walloon attitudes are less outspoken in the Flemish population than anti-immigrant attitudes, are less founded on cultural threat perceptions and are more closely linked to feelings of identification with the Flemish in-group.