The characterization of historical mortars was performed by thermal analysis (TG-DTG), simultaneous infrared spectroscopy (TG-FTIR) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The samples were taken from St. John Church (Tartu, Estonia), built in the 13th-14th centuries. The analyses are important for the restoration of the church. In reality, mortar is a very difficult system, the lime is accompanied with different hydraulic components. TG-DTG analysis and FTIR methods can be used to identify various components of mortar and to observe the reactions associated with the controlled heating at 25-900 degrees C in dynamic air and nitrogen atmosphere. The elemental composition of the acid-soluble components (ASC) was determined by using the ICP-AES techniques.