Lysmata debelius is a territorial species, characterised by forming long-term pair bonds between individuals. This species is popular in the aquarium trade, and although it has culture potential it is not yet raised on a commercial scale. These coral reef inhabitants are considered to be key species in the natural habitat, and their culture is of conservation interest. One of the main causes of death in captivity is due to a disturbance of the pair bond, which results in one individual killing the other. However, the factors that induce this behaviour are not understood. A three-chambered apparatus was constructed to test binary individual recognition. One individual from a pair and one outsider (a stranger), both in similar reproductive state and size, were placed in different chambers. The other individual of the pair was placed in the remaining space, and its behaviour continuously recorded with a video camera during 3 h. The number of visits and the total time spent in the chamber of its mate over a 30-min interval, analysed with a two-way ANOVA, were significantly higher than for the time spent in the stranger's chamber. These results suggest that Lysmata debelius is able to distinguish a partner from a stranger, and this ability appears to remain for at least 3 h after separation.