This article presents the outcome of a series of in-plane shear tests on non-traditional masonry walls under unstrengthened and strengthened conditions. The uniqueness of the experiments arises from the testing of unfired clay and earth (adobe) bricks, which are typical for numerous historical buildings and which have significantly different mechanical properties in comparison with the nowadays commonly used fired bricks, concrete blocks, etc. The applicability and suitability of two different strengthening techniques, which do not require significant structural intervention, were investigated with the use of two evaluation procedures. The first technique was realised using steel wire ropes that were mechanically fastened to the wall and arranged in an X shape. The other technique comprised of the application of a geo-net to the surface of the wall, which was then covered with a layer of adobe plaster. Two different types of geo-nets were tested. The paper focuses on the assessment of the influences of both strengthening techniques in changing the structural resistance of the walls loaded by a combination of constant vertical compression and a cyclic horizontal loading. Other mechanical parameters, e.g. ductility or damping, were also investigated in detail. In addition, the geo-net retrofitting technique applied to a previously damaged wall was studied. Conclusions and practical recommendations for preventive strengthening of adobe and dry brick masonry walls or for remedial work on damaged masonry in regions with high seismic risk are given.