German cockroaches, <i>Blattella germanica</i> (Blattodea: Ectobiidae), are human commensals that move freely between food and waste, disseminating bacteria, including potential pathogens, through their feces. However, the relationship between the microbial communities of the cockroach gut and feces is poorly understood. We analyzed the V4 region of the 16S rRNA gene and the V9 region of the 18S rRNA gene by next-generation sequencing (NGS) to compare the bacterial and protist diversities in guts versus feces and males versus females, as well as assess variation across cockroach populations. Cockroaches harbored a diverse array of bacteria, and 80 to 90% of the operational taxonomic units (OTUs) were shared between the feces and gut. Lab-reared and field-collected cockroaches had distinct microbiota, and whereas lab-reared cockroaches had relatively conserved communities, considerable variation was observed in the microbial community composition of cockroaches collected in different apartments. Nonetheless, cockroaches from all locations shared some core bacterial taxa. The eukaryotic community in the feces of field-collected cockroaches was found to be more diverse than that in lab-reared cockroaches. These results demonstrate that cockroaches disseminate their gut microbiome in their feces, and they underscore the important contribution of the cockroach fecal microbiome to the microbial diversity of cockroach-infested homes.<b>IMPORTANCE</b> The German cockroach infests diverse human-built structures, including homes and hospitals. It produces potent allergens that trigger asthma and disseminates opportunistic pathogens in its feces. A comprehensive understanding of gut and fecal microbial communities of cockroaches is essential not only to understand their contribution to the biology of the cockroach, but also for exploring their clinical relevance. In this study, we compare the diversity of bacteria and eukaryotes in the cockroach gut and feces and assess the variation in the gut microbiota across cockroach p...