The influence of temperature and time parameters of heat treatment on the structure and properties of martensitic-ferritic class steel 15Cr11MoVNb was investigated. The paper analyzes the obtained results of the structural changes in 15Cr11MoVNb steel after homogenization with subsequent thermal improvements in metal of welded joints. It is shown that homogenization at a temperature of 1150°C can significantly reduce the -ferrite content in the steel structure and improve the ductility and plastic properties of steel without changing its strength properties by more than 2 times. Estimation of the distribution of micro hardness of weld metal of the 15Cr11MoVNb steel before and after homogenization and subsequent thermal improvements was revealed. It is established that the proposed thermal treatment eliminates a soft stratum in the weld metal. The investigated heat treatment mode of the 15Cr11MoVNb steel enhances the strength of metal in the heat-affected zone of the welded joint in its entirety, from the line of fusion to the base metal.