As someone who has studied both Old Norse and is pretty damn good at Old English , I would not call them mutually intelligible . Only having a basic grounding in ON , I do find that OE helps me be able to puzzle a lot of things out however , difference in pronunciation , spelling conventions and grammar keep it from perfect mutual intelligibility . Thanks for the response . So to what degree do you think they would understand each other if at all . If you see my above comment , there was a point in the show Vikings where some Englishmen led on like they didn ' t understand a single word the Norsemen were saying , would that be the case ? I ' m very interested in this topic to be quite honest . I ' ve seen the video you ' re talking about with the farmer and the Old English , but the sentences they ' re using are so basic and are almost entirely comprised of cognates , that it ' s not a fair metric on mutual intelligibilty . Modern Frisian and Old English are not at all mutually intelligible . True , true . I appreciate your skepticism ! I just thought the video was cool .