Tobacco smoking and exposure to tobacco secondhand smoke (SHS) can cause lung cancer. We determined uptake of NNK (4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone), a tobacco specific potent pulmonary carcinogen, in hookah smokers and non-smokers exposed to hookah tobacco SHS. We analyzed data from a community-based convenience sample of 201 of adult (aged ≥18 years) exclusive hookah smokers (n = 99) and non-smokers (n = 102) residing in San Diego County, California. Participants spent an average of three consecutive hours indoors, in hookah lounges or private homes, where hookah tobacco was smoked exclusively. Total NNAL [the sum of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides], the major metabolites of NNK, were quantified in spot urine samples provided the morning of and the morning after attending a hookah event. Among hookah smokers urinary NNAL increased significantly (p<0.001) following a hookah social event; the geometric mean doubled, from 1.97 to 4.16 pg/mg. Among non-smokers the increase was not significant (p = 0.059). Post hookah event urinary NNAL levels were highest in daily hookah smokers, and significantly higher than in non-daily smokers or non-smokers (GM: 14.96 pg/mg vs. 3.13 pg/mg and 0.67 pg/mg, respectively). For both hookah smokers and non-smokers, pre-to-post event change in urinary NNAL was not significantly different between hookah lounges and homes. We suggest posting health warning signs inside hookah lounges, and encouraging voluntary bans of smoking hookah tobacco in private homes.