Iran is located on one of the most seismic active areas of the world, and has frequently suffered from earthquakes. Past seismic events have demonstrated that historical vaulted adobe constructions are vulnerable to earthquakes. The historical fabric of Yazd, a city located in the middle of the country, has a vast number of vernacular adobe houses with vaulted adobe roofs still in-use and in an acceptable condition. Hence, considering the historical seismicity of other Iranian World Heritage earthen sites, research is needed to provide seismic safety of adobe heritage in the historic center of Yazd, with respect to the conservation principles of cultural heritage. In order to guarantee the inhabitant’s safety and to improve the strengthening of the vaulted adobe houses under seismic actions, this thesis contributed with a comprehensive preventive conservation procedure, determined by relevant conservation criteria, which contributed to an adequate seismic-retrofitted intervention design. The preventive conservation approach for heritage, located in earthquake prone areas, required evaluating the seismic performance and the adobe houses safety through which the decision on intervention could be made. Accordingly, the main part of this thesis dealt with the seismic safety assessment of the adobe houses, through a combined experimental-numerical research work. First, a representative sample of adobe houses in Yazd was analytically studied using a simplified in-plane assessment method, which is based on three geometric indexes. Concerning the out-of-plane behavior of the studied houses, the limit of the analysis theory implemented in the Block2D software was adopted to perform a parametric analysis on a defined reference model. The results indicated the safe inplane behavior of most of the houses sampled and the safe out-of-plane response of the reference model under gravitational loads. The sample out-of-plane safety under earthquake-induced loads, seems to be a matter of concern. Moreover, an experimental study was performed representing the existing vaults in the adobe houses. Considering the seismic intervention criteria and the safety assessment results, a low cost fiber-glass mesh covered with earth plaster was chosen as the intervention technique. Then, a representative number of adobe vaults, strengthened by the proposed technique, was analyzed experimentally. The results revealed that the proposed technique was able to improve the initial stiffness, load capacity and displacement capacity of the strengthened vaults, when compared with the two unstrengthen vaults. However, the degree of improvement depended on the strengthening strategy followed. The thesis helped substantiate the process of decision-making regarding conservation intervention, which led to the strength of seismic retrofitting on the studied vaulted adobe houses. Current research could also be useful to provide standards and regulations related to the protection of adobe heritage, but could contribute to strength adobe architecture in seismically prone regions.