Existing research has shown that online networks are often segregated along identity lines, such as political ideology or religious views. Although online segregation should be specifically detrimental when appearing between ethnic groups in a post-conflict setting, to date we have no systematic evidence on the level of online ethnic segregation. To close this gap, the present study examines online ethnic segregation in a large ethnically mixed blogger network in a postconflict society, Bosnia and Herzegovina. Since politics has been found to enhance ethnic divides in the offline world, we additionally examine whether segregation is higher for bloggers engaging with political topics. Using large-scale web scraping, automated text analysis and Monte Carlo simulation, we find evidence for pronounced ethnic divisions. Furthermore, we find that political bloggers tend to have more ethnically segregated networks. The findings show that a broad public exchange transcending ethnic categories remains limited in the online context we study, and that those who dominate the online political debate tend to be those who in their social interactions put even more weight on ethnic categories than the average.