Males of Pagurus middendorffii show precopulatory guarding behaviour, and male-male contests often occur between the guarding male and intruder. Intruders use self-assessment in the pre-fight phase of contest and mutual-assessment during the fighting phase. Males of this species also seem to be able to identify a specific female when they often encounter with each other. Intruders may use information of individual identification of opponents and/or females guarded by the opponents in the past contests to determine the behaviour during the subsequent contest since such identification would be beneficial because of reducing the fighting costs. To examine this hypothesis, we observed mate contests during two consecutive periods. When intruders lost in the first contest, we used them in the second contest where the guarding pairs were (1) familiar pair, (2) familiar female and unfamiliar male with winning experience or (3) unfamiliar naïve pair. In the presentation, we will discuss the effects of the prior experience and the familiarity of the opponents on the behavioural decision of intruders.