The first reinforced concrete buildings in Mexico were constructed at the beginning of the 20th century. The introduction of the Hennebique construction system, which combined steel structural elements and cement mortar, by Rear Admiral Ángel Ortiz Monasterio and Naval Engineer Manuel Rebolledo, marked the beginning of modern architecture in Mexico. These buildings still exist today and need to be assessed and rehabilitated to comply with current construction regulations. However, although reinforced concrete is still one of the most important construction materials in this country, heritage reinforced concrete buildings cannot be assessed or rehabilitated in the same manner as contemporary concrete structures. This paper describes a structural assessment methodology that considers the current state of the building and its construction materials such as concrete, reinforcing steel, and masonry, using destructive and non-destructive tests. Based on this information, retrofitting techniques that enhance the building’s strength should be implemented in accordance with the recommendations of ICOMOS and ISCARSAH, with the aim of preserving the intrinsic and architectural values of these structures.