© 2021, Istanbul Teknik Universitesi, Faculty of Architecture. All rights reserved.Within the 20th century, the National Architectural Period in Turkey began and the structures which had mixed systems with reinforced concrete (RC) and masonry was seen commonly. This period is also called “Modernization” and the buildings were considered as Modern Architectural Heritage structures. Since most of these buildings are used today, conservation and restoration attempts have become more essential to maintain safety conditions for users with the cultural heritage value of the buildings. Some parameters should be taken into account like the material properties, environmental conditions and human activities that are more effective in the degradation of the structures. However, the conservation and restoration of mixed structures are less investigated in literature because these structures have complex construction techniques and there are not definite rules in the related regulations. So, these kinds of articles that present the studies can be seen invaluable for the structures which has similar problems and solutions. This paper presents in-situ examination and laboratory analyses on the building materials used in Istanbul University Buildings accepted as a cultural heritage masonry infilled RC structure. First of all, in-situ examination was done according to the observations on the exterior and interior walls, Secondly, representative material samples taken from different locations of the buildings both masonry and the RC sections. For the determination of the properties and deteriorations of the materials, the chemical analyses and the physical and mechanical tests were conducted. According to the results, the conservation and restoration applications were recommended for the case study buildings.