Texture and microstructure evolution in a ferritic/martensitic 9wt%Cr oxide dispersion strengthened (ODS) steels during heat treatment after cold tube forming are studied via in situ synchrotron X-ray diffraction analysis. The initial textures of cold-formed ODS steel tubes present a well-known alpha-fiber (< 110 >//RD). During high-temperature heat treatment, this initial sharp fiber texture, inherited from cold forming, is transformed by the phase transition to austenite into a weak < 111 > fiber. During cooling, a texture memory effect is observed with a strong dependency of the fiber intensity on the cooling rate. After quenching into martensite, the < 110 > fiber becomes weaker than in the initial ferrite. By contrast, after slow cooling into ferrite, the < 110 > fiber develops and becomes stronger than initially. For many materials, texture memory effect can be explained by a variant selection phenomenon. Accordingly, experimental results are compared to the double Kurdjumov-Sachs (DKS) model. During heating, a limited texture heritage is exhibited with essentially a Kurdjumov-Sachs (K-S) relation between the two phases. During cooling the DKS relation correctly predicts the texture fiber components. However, the strong enhancement of texture during slow cooling remains not completely explained. A Williamson-Hall analysis of the size and strain evolutions during the heating cycle showed a remarkable stability of the crystallites size which is the same in ferrite, austenite and martensite.