Thermal conductivity, thermal diffusivity were measured in the atrium of a swine heart. Radiofrequency (RF) catheter ablation in an atrium has rapidly emerged at the treatment of symptomatic reentrant arrhythmia associated with accessory pathway or Atrioventricular (AV) node conduction. The thermal properties of an atrium are definitely necessary for these treatments because, in thermal treatments, conductivity and diffusivity are significant factors in the relationship between the applied RF power and the resulting atrium temperature rise. Thermal properties were measured using a self-heated thermistor probe. Thermistor probes were inserted into the tissue of interest and were used to supply heat within the tissue as well as to monitor the temperature rise in the tissue. The measurements were performed at temperatures of 25, 37, $50^{circ}C$. Atrium thermal conductivity ranged from 5.17$pm$0.12 mW/cm$^{circ}C$ at $25^{circ}C$ to 5.33$pm$0.08 mW/cm$^{circ}C$ at $37^{circ}C$. Atrium thermal diffusivity ranged from 0.00132$pm$0.00007$cm^2$/sec at $25^{circ}C$ to 0.00138$pm$0.00003 $cm^2$/sec at $50^{circ}C$. This paper also present the thermal property comparison of both chambers of a heart (ventricle and atria).