AbstractGlobalization has facilitated the introduction and establishment of organisms beyond their natural ranges, leading to significant ecological and economic consequences. While many non‐native species are well documented, others remain understudied, either due to their unknown impact or morphological similarities with native species. This study addresses such a case, focusing on synanthropic cockroaches within the order Blattodea. Despite the order's diversity, less than 1% of known species are recorded in urban environments. While certain species like Periplaneta americana, Blatta orientalis and Blattella germanica are well distributed and studied, others remain largely unknown. This research unveils the first established population of Nauphoeta cinerea in Europe, specifically in Spain (Asturias, northern Iberian Peninsula), with specific genetic and morphological confirmation. This study also explores potential pathways of introduction for N. cinerea. Long‐distance transport by ships or escape/release from captivity are proposed as potential pathways for the newly established populations in Asturias. The species' high fecundity and parthenogenetic reproduction raise concerns about its potential invasiveness. Additionally, this study includes unpublished data on various synanthropic cockroaches in Asturias (with the first records of P. lateralis and Supella longipalpa for this area), drawn from specimens deposited in biological collections and some extra collections. An identification key for all Spanish non‐native synanthropic cockroach species is provided to assist in future detections. This research emphasizes the imperative need for robust monitoring systems, highlights the scarcity of scientific information regarding synanthropic cockroach distribution and underscores the pivotal role of biological collections in advancing our understanding of invasive species.