The introduction of a thermo-Viscous Fluid (TVF) between two skins, produces a sandwich with high dissipation. This was studied by Hussain and Guyader [An equivalent plate model for sandwich panels with thermoviscous fluid core, J. Vibration Acoustics, ASME trans., 031007 (2012)] leading to equivalent material properties depending on skins and fluid core properties. An important result is that contrary to standard sandwich panels with polymers cores, the damping loss factor of such TVF sandwich is constant with frequency. When applying damping treatment on structures, bonded patches are generally used. In this paper the use of TVF sandwich patches on a panel is described through a model of heterogeneous plate, the predicted vibration response of the structure shows an increase of damping due to the patch. Estimation of modal damping loss factors for the plate with TVF sandwich patches are given depending on the patch size and TVF thickness.