Background: The increasing incidence of cancer among young adults (18–40 years old) is of concern in China. Objectives: This study aims to examine the influence of cancer information-seeking behaviours (CISB) on young adults’ worries about cancer and participation in screening. Methods: This study analysed data from two probability sample surveys conducted in 2012 and 2017 in China. The questions in the questionnaire remained the same for better comparison. The sample size was 1212 in the 2012 survey, and 2178 in the 2017 survey. Results: From 2012 to 2017, among young adults, there was a decline in cancer information seeking, diversity of cancer information sought and cancer worry, while an improvement in cancer information-seeking experience was found. Also, CISB had significant associations with cancer worry and health screening over the 5 years. Discussion: The level of young adults’ cancer information seeking remains low in China, and this group is not fully aware of their potential risks of getting cancer. Conclusion: Although young adults find the experience of looking for cancer information easier in 2017, health campaigns may be necessary to encourage young adults to find out more about their cancer risks, and to participate more in health screening.