CoCrFeMnNi type alloy with reduced Cr content and addition of 2 at. % C was processed by high pressure torsion (HPT). Uniform nanocrystalline single fcc phase microstructure was present in as-deformed alloy [1]. Subsequent post deformation annealings were conducted in temperature range 200-600 °C for 1 h. A sequence of precipitation – dissolution of secondary phases reactions was observed starting at 500 °C. At that temperature minor grain growth was accompanied by the precipitation of CoFe and NiMn phases, whereas Cr segregated at grain boundaries. Significant increase of the precipitates volume fraction and notable grain growth were observed after annealing at 530 °C for 1 h. Cr-rich carbides formed at grain boundaries. CoFe and NiMn phases were identified using HR-STEM combining micro probe diffraction characterization. CoFe phase shows a chemically ordered structure with a few substitutions known as B2 phase, while NiMn phase has a tetragonal structure with chemical disordering. After annealing at 600 °C for 1 h, CoFe phase and NiMn phases re-dissolved in the fcc matrix and Cr-rich carbides evolved to M7C3 type carbide. The mechanical properties of nanocrystalline HEA resulting from thermal treatment will be presented and discussed.