In Latin America, a significant portion of the existing built stock consists of earthen structures, many of which hold heritage value. These buildings exhibit high stiffness and minimal structural drift, allowing them to absorb substantial shear forces during seismic events. However, they are particularly vulnerable to diagonal tension failures, especially in short walls. Existing reinforcement techniques often fail to meet heritage retrofit guidelines requiring material compatibility and minimal alteration. Effective retrofitting solutions are essential to enhance the structural performance of these buildings and extend their service life. This study proposes a method to improve the shear strength of short earthen walls by applying an external guadua-bamboo mesh reinforcement. A mechanical external anchorage procedure is also evaluated to facilitate retrofitting while preserving heritage structures. The research focuses on common masonry wall types in Ecuador and Colombia, including those constructed from earth blocks (adobe) and rammed earth (tapial). Two full-scale earthen walls, each with an aspect ratio of 1:1, were retrofitted using guadua-bamboo mesh reinforcement and subjected to quasi-static lateral loading tests. The results indicate that this retrofit method effectively mitigates shear failure, enhances lateral displacement capacity, and promotes a more resilient rocking response. While the retrofitted adobe wall did not show an increase in lateral strength, this retrofit contributed to improved wall stability. Moreover, the retrofitted rammed earth wall did not exhibit shear cracks and primarily responded with rigid block rocking.