Characterization of mortars and plasters used in historical structures is crucial before conservation interventions in order to propose proper repair materials and avoid any damage caused by material incompatibility. In the present study, mortars and plasters of a Byzantine Church in the ancient city of Stratonikeia dated back to 5th-7th centuries were examined in terms of physical/physico-mechanical characteristics and raw materials used by various analytical techniques. Possible use of pozzolanic materials in mortar and plaster samples were investigated by pozzolanic activity tests performed on the aggregates (< 125 mu m) and examining the reaction products formed after immersion of these aggregates in a saturated solution of Ca(OH)(2). Investigated mortar and plaster samples were found to have relatively low bulk density and high effective porosity. Compressive strength values of mortar samples were found to be in the range of 3.92-4.47 MPa. Binder used in the mortar and plaster samples were assessed to be fat lime. Aggregates of the samples smaller than 125 mu m were found to have good pozzolanicity. Formation of pozzolanic reaction products by the reaction of the finer aggregates with Ca(OH)2 were confirmed by the results of SEM-EDX and FTIR analyses.