This study investigates the relationship between cancer information-seeking, cancer risk perception, and cancer fatalism among young and older adults. It aims to examine whether cancer information-seeking affects cancer fatalism through the mediation of cancer risk perception. This cross-sectional study used secondary data from the Health Information National Trends Survey (HINTS 6). The sample included 2865 older adults (aged ≥ 60) And 1476 young adults (aged ≤ 40). Data were analyzed using SPSS (version 26), and mediation effects were examined using Hayes' PROCESS macro (version 4.3, Model 4). The direct relationship between cancer information-seeking and cancer fatalism was not significant in either the young or older adult groups. However, cancer information-seeking significantly reduced cancer fatalism by lowering cancer risk perception in both groups (older adults: β = -0.01, SE = 0.004, 95% CI [-0.02, -0.004]; young adults: β = -0.03, SE = 0.01, 95% CI [-0.05, -0.02]). The effect was stronger in the young adult group, suggesting that young adults are more influenced by information-seeking behavior in changing their cancer risk perceptions. This study highlights the importance of cancer information-seeking behavior in mitigating cancer fatalism, with risk perception playing a crucial mediating role. The findings indicate that the act of seeking cancer information helps alter perceptions of cancer risk. This effect was more pronounced in young adults compared. The results suggest that interventions aimed at encouraging cancer information-seeking could be effective in shifting risk perceptions, thereby reducing fatalistic attitudes toward cancer.