The rammed earth technique has a significant presence in the earthen built heritage, where it served to build from simple dwellings to fortresses. However, the high vulnerability of rammed earth constructions to decay agents and to seismic events puts at risk their further existence and the lives of millions of people. With respect to the seismic behaviour of rammed earth walls, the understanding and modelling of their shear behaviour are topics rarely approached in literature. Nevertheless, these topics are of extreme importance in the preservation and strengthening of rammed earth constructions. This paper presents an experimental and numerical work where the shear behaviour of unstabilised rammed earth (URE) is analysed. The experimental program consisted in the testing of several URE wallets under diagonal compression, which allowed a better understanding of the shear behaviour of URE. The numerical work consisted in the modelling of the previous tests by the finite element method and by considering both the macro- and micro-modelling approaches. In general, the numerical models showed a good agreement with the experimental results.