This study evaluated the association between tobacco smoking and bladder cancer risk in a large prospective cohort of men and women in the United States. The NIH-AARP Diet and Health Study, initiated in 1995 and followed through 2006, included 281,394 men and 186,134 women. During 4,518,938 person-years of follow-up, 3,896 men and 627 women were diagnosed with bladder cancer. Former and current smokers had significantly higher risks of bladder cancer compared to never smokers, with relative risks (RR) of 2.22 (95% CI: 2.03–2.44) for former smokers and 4.06 (95% CI: 3.66–4.50) for current smokers. The population attributable risk (PAR) for ever smoking was 0.50 (95% CI: 0.45–0.54) in men and 0.52 (95% CI: 0.45–0.59) in women. The study found higher risk estimates for current cigarette smoking compared to previous studies initiated between 1963 and 1987, suggesting that the association between smoking and bladder cancer may have strengthened over time, possibly due to changes in cigarette composition. These findings highlight the continued importance of tobacco control efforts to reduce bladder cancer incidence.This study evaluated the association between tobacco smoking and bladder cancer risk in a large prospective cohort of men and women in the United States. The NIH-AARP Diet and Health Study, initiated in 1995 and followed through 2006, included 281,394 men and 186,134 women. During 4,518,938 person-years of follow-up, 3,896 men and 627 women were diagnosed with bladder cancer. Former and current smokers had significantly higher risks of bladder cancer compared to never smokers, with relative risks (RR) of 2.22 (95% CI: 2.03–2.44) for former smokers and 4.06 (95% CI: 3.66–4.50) for current smokers. The population attributable risk (PAR) for ever smoking was 0.50 (95% CI: 0.45–0.54) in men and 0.52 (95% CI: 0.45–0.59) in women. The study found higher risk estimates for current cigarette smoking compared to previous studies initiated between 1963 and 1987, suggesting that the association between smoking and bladder cancer may have strengthened over time, possibly due to changes in cigarette composition. These findings highlight the continued importance of tobacco control efforts to reduce bladder cancer incidence.