The purpose of this study was to describe the cancer-screening intention, sources of cancer information, and cancer understanding among Japanese adolescents. A cross-sectional nationwide survey involving a self-administered questionnaire was conducted. Response rates of the target schools were 46.4 % (n = 103) for junior high schools and 55.8 % (n = 116) for high schools. From these, we analyzed the data of 2960 junior high school students (1520 males, 1440 females) and 3703 high school students (1546 males, 2157 females) to examine the association between cancer-screening intention and sources of cancer-related information and understanding. A significant association between cancer-screening intention and sources of cancer information and cancer understanding was observed. The screening intention group identified more sources of cancer information than the no-screening intention group did. Understanding about cancer was reported by a higher proportion of students in the screening intention group compared with the no-screening intention group. Recognition that healthy people must take part in cancer screening was significantly associated with screening intention in both junior high (odds ratio (OR), 1.859; 95 % confidence interval (CI), 1.582–2.185; P < 0.001) and high school (OR, 2.485; 95 % CI, 2.139–2.887; P < 0.001) students. Health education at school was indicated by a high proportion of students as a source of cancer-related information, although the association was not significant. The present survey indicated that those in of our sample who intended to undergo future cancer screening (67.8 %) had more sources of information and understanding regarding cancer. Thus, schools should enrich health education curricula with more information and understanding about cancer to promote cancer-screening intention among Japanese adolescents.