Abstract Background: Childhood cancer affects patients and their parents. Childhood cancer survivors are at risk of mental health problems. Regular psychological screening is recommended. The emotion thermometer (ET) is a short, validated tool to detect psychological distress in adult patients with cancer. However, its suitability and acceptability in young cancer populations have not yet been reported. We (1) describe mental health in survivors and their parents before and after a follow-up appointment and (2) investigate the ET's usefulness for screening in young childhood cancer survivors. Methods: Survivors (15 years or older at study, ≥1 year after treatment ended) and their parents completed two electronic surveys to assess mental health (including somatization, depression, anxiety, a Global Severity Index [GSI], fear of cancer recurrence/relapse and post-traumatic stress). The first questionnaire was completed in the weeks leading up to the follow-up appointment and the second one after. We assessed survivors' opinion on acceptability of the ET. Results: Forty-five survivors (age at study: 22 years, 54% female) and 46 parents (age: 54 years, 63% female) participated. Scores for somatization, depression, and the GSI were lower after the appointment (p<.05 for all). For parents, there was no change. A subset of survivors reported clinically relevant post-traumatic stress (Nbefore = 3 [8%], Nafter = 4 [10%]). Fear of cancer recurrence/relapse remained stable. The ET identified moderate-to-severe distress in 13 survivors (29%), showing good specificity (0.91) and sensitivity (0.91) in relation to the gold standard Symptom Checklist-90-R. Survivors found the ET to be easy to use and understand. Conclusions: Psychological distress in survivors attending follow-up care is common, and screening is imperative. The ET may be helpful for initial psychological screening.