The amount of cancer-related information available to the general population continues to grow; yet, its effects are unclear. This study extends previous cross-sectional research establishing that cancer information seeking across a variety of sources is extensive and positively associated with engaging in health-related behaviors. The authors studied how active information seeking about cancer prevention influenced three healthy lifestyle behaviors using a 2-round nationally representative sample of adults ages 40-70 years (n = 1,795), using propensity scoring to control for potential confounders including baseline behavior. The adjusted odds of dieting at follow-up were 1.51 (95% CI: 1.05, 2.19) times higher for those who reported baseline seeking from media and interpersonal sources relative to nonseekers. Baseline seekers ate 0.59 (95% CI: 0.28, 0.91) more fruits and vegetable servings per day and exercised 0.36 (95% CI: 0.12, 0.60) more days per week at 1-year follow-up compared with nonseekers. The effects of seeking from media and friends/family on eating fruits and vegetables and exercising were independent of seeking from physicians. The authors offer several explanations for why information seeking predicts healthy lifestyle behaviors: information obtained motivates these behaviors; information sought teaches specific techniques; and the act of information seeking may reinforce a psychological commitment to dieting, eating fruits and vegetables, and exercising.