According to the British Library's Medieval Manuscripts page, certain medieval manuscripts feature a zombiesh tale.
The Three Living and the Three Dead is a kind of pre-Scrooge-like tale in which the three living persons encounter the three "living dead" in varying stages of decay who warn them about the fleeting time of life and to amend their ways before it is too late. Read more about the tale and see more art at the British Library page. You can also see more manuscripts at their Digital Library.
(Manuscript: British Library)