Assenay is located some 12 km south of Saint-André-les-Vergers and 4 km east by north-east of Villery. Access to the commune is by the D1 23 road from Saint-Jean-de-Bonneval in the south-west passing through the village and continuing to Villy-le-Maréchal in the north-east. The D 25 road from Saint-Jean-de-Bonneval to Moussey also passes through the north of the commune. Apart from a few scattered patches of forest the commune is entirely farmland.[3]
The Mogne river flows through the south of the commune from south-west to north-east. The Ruisseau d'Ormont flows eastwards through the village to join the Mogne east of the commune.[3]