Adolescent and young adult (AYA) cancer patients may be at high risk of experiencing psychological distress because their diagnosis came during a key time of consolidation of identity and social growth. This study aimed (1) to examine the prevalence of psychological distress among AYA cancer patients within a year of diagnosis to long-term survivors and (2) to describe socio-demographic and cancer-related characteristics associated with psychological distress.

In a cross-sectional web-based survey, patients who scored 5 or more on the Kessler Psychological Distress Scale were assessed for significant psychological distress. Logistic regression examined whether demographics, clinical variables, and social support were associated with psychological distress.

A total of 206 young adult cancer patients participated. The median age at the survey was 34.5 years (range: 22–39 years), and 87.4% were female. The prevalence of psychological distress was 55.3%. Psychological distress among patients diagnosed within a year and long-term survivors (≥10 years since diagnosis) was significantly higher than patients 1–4 years since diagnosis. Pain, decrease in income after a cancer diagnosis, experience of negative change in work/school after a cancer diagnosis and poor social support were significantly associated with psychological distress.

Over half of young adult patients had significant psychological distress in Japan. Our findings potentially contribute to the intervention components for distress management among AYA cancer survivors.