Neutron Bragg-edge imaging was applied for the visualization of a gamma-austenite to alpha'-martensite phase transformation. In the present study, a super martensitic stainless steel sample was heated until complete austenitization and was subsequently cooled down to room temperature. The martensitic phase transformation started at M (s) = 190 A degrees C. Using a monochromatic neutron beam with lambda = 0.390 nm, the transmitted intensity was significantly reduced during cooling below M (s), since the emerging martensitic phase has a higher attenuation coefficient than the austenitic phase at this wavelength. The phase transformation process was visualized by filming the transmission images from a scintillator screen with a CCD camera with a temporal resolution of 30 s and a spatial resolution of 100 A mu m.