Smith waxa uu ku dhashay September 25, 1968 Philadelphia, Pennsylvania, waxaana dhalay Caroline (Bright), oo ah maamulaha dugsiga Philadelphia, iyo Willard Carroll Smith Sr., oo ah halyeey ciidamada cirka Mareykanka ah iyo injineer qaboojiye. Wuxuu ku soo koray xaafada Wynnefield ee Galbeedka Philadelphia, waxaana lagu barbaariyay Baabtiista. Wuxuu leeyahay walaasheed ka weyn oo la yiraahdo Pamela iyo laba walaalo ah oo ka yar, mataano Harry iyo Ellen. Smith wuxuu dhigtay Our Lady of Lourdes, oo ah dugsi hoose oo gaar ah oo Katooliga ah oo ku yaal Philadelphia. Waalidiintiisa way kala tageen markii uu ahaa 13, laakiin dhab ahaantii ma aysan furiin ilaa 2000. Smith wuxuu dhigtay Dugsiga Sare ee Overbrook. In kasta oo si ballaaran loo soo sheegay in Smith uu diiday deeq waxbarasho oo uu ku dhigto Machadka Teknolojiyada ee Massachusetts (MIT), waligiis ma uusan codsan jaamacadda maxaa yeelay "wuxuu doonayay inuu kufsado". Smith wuxuu sheegay in lagu oggolaaday barnaamijka diyaarinta xagaaga [injiinka] ee
dhibcaha sare ee imtixaanka