Wall paintings are the reflections of the lifestyle, sense of art and technology of their own period. Conservation of wall paintings should be considered as a multidisciplinary process which is comprised of documentation, materials characterization, evaluation of deterioration problems and conservation decisions. This study aims to determine the material characteristics and execution techniques of historic wall paintings executed in Byzantine era in western Anatolia. Within this scope, the stratigraphy, mineralogical and chemical composition of the plaster layers; the execution technique, stratigraphy, mineralogical and chemical compositions of paint layers of wall paintings from the substructure of Anaia Church, Başpınar Church and Aigai have been determined by Polarized Light Microscope (PLM), Scanning Electron Microscope coupled with XRay Energy Dispersive System (SEM-EDS), X-ray diffraction analyses (XRD), Fourier transform infrared spectrometry (FT-IR) and Laser Induced Breakdown Spectroscopy (LIBS) analyses. Through the research, pure lime and aggregates in the plasters of Aigai, magnesium rich lime and straw in the plasters of Anaia and Başpınar have been determined. Execution technique used in wall paintings are determined as fresco in Aigai and as secco in Anaia. In Başpınar church painting was started as fresco but completed as secco. Pigments used in paintings are mainly iron oxides for red and yellow, green earth in celadonite and glauconite forms for green, lapis lazuli and Egyptian blue for blue, calcite and kaolin for white and carbon black for grey and black colors. Results of the experimental studies are also evaluated for dating the wall paintings. As a result, studied wall paintings were classified as pre-iconoclastic and post- iconoclastic. Painting technique, pigments and plaster characteristics of wall paintings in western Anatolia in Byzantine period were determined to be similar with the ones in İstanbul, Cappadocia, Balkans, Crete, and Cyprus. Results of this study will guide the conservation efforts of the wall paintings.