An haifi Smith Sadie Smith a Willesden a cikin yankin arewa maso yammacin London na Brent zuwa mahaifiyar Jamaica, Yvonne Bailey, da mahaifin Ingilishi, Harvey Smith.A lokacin da yake da shekaru 14, ta canza sunanta zuwa Zadie.Uwar Smith ta girma a Jamaica, kuma ta yi hijira zuwa Ingila a shekarar 1969. Iyayen Smith sun saki lokacin da take matashi. Tana da 'yar uwa, dan uwanta, da' yan uwan biyu (ɗaya shine rapper da kuma dan wasan kwaikwayo na Doc Brown, ɗayan kuma shine rapper Sky Lucz).
sa'ad da take matashiya