The present invention relates to a novel polymorph of Quetiapine fumarate and a process for its preparation. The novel polymorph of quetiapine fumarate of the present invention has been designated by us as Form IV. The quetiapine fumarate is salt of 2-[2-(4-dibenzo [b,f]][1,4] thiazepin-11-yl-1-piperazinyl) ethoxy]-ethanol with fumaric acid (2:1). It is also referred as hemifumarate in some patent literature. Its complete structure is shown below: