Previous research has demonstrated that, irrespective of prior familiarity, both social and solitary rodent species respond differentially to odours of other individuals based on the degree of genetic relatedness between them. To investigate whether eusocial species also make odour-based genetic relatedness discriminations, male and female Ansell’s mole-rats (Cryptomys anselli) were exposed to ano-genital odours of unfamiliar opposite-sex conspecifics (one unrelated individual and one “estranged” sibling, from whom they had been separated for 27 days). Habituation tests with the odours of “estranged” siblings and courtship tests confirmed that the “estranged” siblings and their odours were treated as unfamiliar. Subjects spent significantly more time investigating unrelated individuals and their odours, than their “estranged” siblings and their odours, indicating discriminative behaviour toward less genetically similar individuals. The findings suggest that eusocial mole-rats can respond differentially to odours based on their degree of relatedness to the odour donors.