In sheep, the bond between the dam and her lambs is established during the first hours of a lamb's life. Genetic variability for behavioural reactivity of ewes assessed in an arena test performed 24 hr after lambing has already been reported. However, there is no evidence that this reactivity represents the ewe's maternal reactivity at lambing in outdoor conditions. The objective of this study was to investigate whether or not the behavioural reactivity of ewes in the arena test is genetically related to their maternal reactivity measured at lambing. A total of 935 Romane ewes were studied. The maternal reactivity of ewes at the outdoor lambing site was recorded in response to a human approach and to the handling of the lambs. Their behavioural reactivity was also recorded 24 hr post-lambing in the arena test that involved a separation from the litter and a human presence. Flight distance, aggressive reaction, time to restore contact with the litter, maternal behaviour scores and vocalizations recorded at the lambing site were heritable (0.12-0.34). All of these behaviours were genetically correlated with the behavioural reactivity in the arena test. The highest genetic correlations (from 0.60 to 0.90) were found amongst maternal behavioural scores, flight distance and high-pitched bleats. In conclusion, behavioural reactivity in the arena test can be used to assess early maternal reactivity in standardized conditions. Phenotyping of ewes' behavioural reactivity with a simplified arena test can be performed for genetic improvement in maternal behaviour in sheep.