Adobe constructions account for a significant portion of the built heritage, associated with early building techniques, material accessibility and low-cost. Nonetheless, adobe buildings, due to their low mechanical properties and overturning resistance, are subject to early structural damage, such as cracking, separation of structural elements and, possibly, collapse in areas of high seismic hazard. The lack of maintenance and absence of adequate retrofitting techniques usually intensifies the loss of historic fabric. The current paper, aims at the structural assessment and seismic safety, in current conditions, of the Church of Kuño Tambo, a religious adobe structure of the 17 th century, in Cusco region, in Peru. The inspection and diagnosis involved sonic testing and damage mapping, while ambient vibration tests revealed the modal response of the structure. The assessment of seismic vulnerability, together with the necessity of retrofitting measures were verified through nonlinear static and pushover parametric analyses, complemented with a macro-block limit analysis and a performance based assessment, under local seismic criteria. A more realistic response from dynamically induced ground motions was performed, by a nonlinear time history analysis, according to the Eurocode 8 framework. Through an integrated approach, in situ inspection, testing, numerical and 2 analytical modelling are associated under the scope of reproducing the existing structural damage, the sequence of inelastic behavior and verification of the necessity of retrofitting measures. based approach. Short Title: Seismic vulnerability of earthen historic structures walls, out-of-plane mechanisms can involve smaller portions of the walls. The lateral resistance is related to the compressive strength of adobe masonry and to the effective compressive area of the cross-section, which counteracts the inertia destabilizing forces [Tomazevic 1999]. Thus, the compressed part of the rotation plane is often crushed under compression (toe crushing) ["OPCM 3431" 2005, "NTC" 2008]. Yet, in specific adobe historic structures, composed by walls of large width and low in height, the compressive strength is not much influencing the maximum load capacity, as shown in this work. Adobe structures have a compressive strength in the range 0.5-3 MPa, with the modulus of elasticity being usually lower than 1 GPa, thus experiencing high deformations and relatively brittle failures ["NIKER" 2010]. When box behavior is present, out-of-plane vertical cracks can still be formed, due to bending at the corners and in the middle of the walls. But, in-plane bending and mostly shear, cause horizontal, vertical and diagonal cracks. Damage mechanisms depend mainly on the geometry of the wall (height/width ratio), boundary conditions and additional vertical loading. The presence of discontinuities and openings are also influential, with shear cracks forming in the proximity of spandrel beams and at the corners of openings. In-plane damage can also be the result of interaction or...