The creator of TWD comic book series, Robert Kirkman confirmed the news at New York Comic-Con, reported The Independent.
Kirkman said the much-awaited event see one character appear in both shows but did not reveal who will he/she be.
"There is one character that is going to go from one show, that I will not name, to another show, that I will not name. This is a huge event in the world of 'The Walking Dead'," he said.
"The Walking Dead" season eight starts on October 22, while the third season of "Fear The Walking Dead" will end on October 15.