Abstract <p>Gravity and magnetic fields studies have been conducted in the area of the Verkhne-Koshelevskaya thermal anomaly. Maps of the Bouguer gravity anomalies Δ<i>g</i> and anomalous magnetic field Δ<i>T</i>_a are obtained. Probable two-dimensional (2D) grid models of the source structure of the thermal anomaly down to a depth of 500 m are constructed and described. The structure creating the thermal field is characterized by the presence of areas with different density and magnetic characteristics, and the structure of the field is heterogeneous. It was established that the most active and high-temperature segment, Tartarary, at the upper reaches of the Vostochnyi Creek has low density (up to 1.9–2.0 g/cm³) and magnetization (–0.5 A/m). This segment is likely confined to a permeable zone of tectonic faults.</p>