Wefensleben is situated on the river Aller, in the lowland between the foothills of the Lappwald and the Osterberg (166 m (545 ft)).

In the west is a forest of 24 ha (59 acres) named "Trenckmann's Busch" or "Zechenholz".

The first documentarily mention occurred in the year 1160 in the property list of the St. Ludger's Abbey in Helmstedt (German: Kloster St. Ludgeri).

In the 1970s several Plattenbauten were built in the village and Wefensleben became a sleep and living place for the attendants of the Helmstedt–Marienborn border crossing and their families.

At this time many members of the Stasi moved to Wefensleben especially attendants of the Passkontrolleinheit (PKE) a division of the former Eastern Germany secret service who worked at the border crossing.