This paper presents the results of studies on texture formation in ferritic/martensitic steel 12Cr-2W subjected to equal channel angular pressing, warm rolling, and additional heat treatment. X-ray diffraction analysis, transmission electron microscopy, and electron backscatter diffraction were used to study the structure. An unusual texture transition H {001} <110> fi L {0 11} <011> was observed for the first time during additional heat treatment of rolled ferritic/martensitic steel. A possibility of such texture transition is due to activation of twinning processes and increase of a number of boundaries with the coincidence site lattice relationships (the CSL boundaries).