Itardies, a locality dated around 30 million years ago in the Phosphorites of Quercy, yielded an exceptional quantity of fossil remains attributed to Amphicynodon leptorhynchus, a little-known and yet emblematic small carnivorous mammal of these fossiliferous sites in southwestern France. Among the Carnivora, the extinct family Amphicynodontidae derives from the first evolutionary radiation of the clade Arctoidea. Although they were notably important and diverse extras in the Early Oligocene Eurasian fauna, members of this family received little attention: their paleoecology and behavioural diversity remain largely unexplored. For the first time, an almost complete composite skeleton of Amphicynodontidae has been reconstructed. Therefore, the detailed functional analysis of its appendicular skeleton allowed to take the first steps in the exploration of its locomotor adaptations and its paleoecology. Combining the results of our functional anatomy study and the study of comparable modern carnivores (posture, myology, coat patterns), we present the restoration process of Amphicynodon leptorhynchus. The resulting image is that of a small, arboreal, crepuscular predator, about 2 kg, able to climb with agility and control. Like modern climbing carnivorans, it moved on the ground with a slightly crouched posture, accentuated when moving through trees and rocks. It was probably able to climb and descend headfirst from a vertical support, leap between branches, or capture prey in trees.