This study examines the properties of the lime mortar and plaster of Isa Bey Bath, Kale Altı Bath, and Yahşi Bey Bath, the last bath buildings that preserved their authentic material structure from the Aydınoğulları Principality in Selçuk. The basic physical properties, raw material, chemical and mineralogical composition, pozzolanic and hydraulic properties of the mortars and plasters were investigated using RILEM standard test methods, SEM-EDS, XRD, and TGA. The interior walls of the baths exhibit two distinct plaster layers in different colors at the lower and upper levels. Lower-level plasters consist of plaster with natural stone aggregate and Horasan plaster, while upper-level plasters consist of plaster with natural stone aggregate and/or lime plaster. The average density and porosity values of Horasan plasters and plaster with natural stone aggregate were 1.71 - 1.48 g/cm³ and 26.83% - 30.70%, respectively. Plasters with natural stone aggregate have higher lime content and lime/aggregate ratio. The natural aggregates used in the mortars and plasters were derived from a raw material source containing minerals of volcanic origin. Brick aggregates were manufactured using low calcium clay at temperatures below 850 ºC. Mortars and plasters have hydraulic characteristics due to the pozzolanic properties of the aggregates used. Basic physical, chemical, and mineralogical compositions and hydraulic properties of mortars and plasters did not have significant differences according to the buildings. The use of raw materials and production techniques with similar properties to produce hydraulic mortars and plasters in historical bath buildings for many years indicates the continuity of local knowledge