BackgroundBoth testicular germ cell tumours (TGCT) and neurodevelopmental disorders are associated with urogenital malformations. Few studies have investigated the association between psychiatric disorders and TGCT. We investigated whether history of any psychiatric or neurodevelopmental disorder is associated with increased risk or mortality of TGCT.MethodThis is a nested case–control study including 6166 TGCT patients diagnosed during 1992–2014, individually matched for age and calendar period to 61,660 controls. We calculated odds ratios (ORs) for the association between type of psychiatric diagnoses and TGCT risk. Among the cases, we used a cohort design and calculated hazard ratios (HRs) of the association between psychiatric diagnose and all-cause and TGCT-specific death.ResultsHistory of a neurodevelopmental disorder (attention deficit hyperactivity disorder, autism spectrum disorder and intellectual disabilities) was associated with an increased risk of seminoma (OR: 1.54; 1.09–2.19). Seminoma patients with neurodevelopmental disorders were younger (34 versus 38 years,p= 0.004) and had more stage IV disease (5.4% versus 1.2%) than those without. Psychiatric history overall was not associated with TGCT. Patient history of any psychiatric disorder was associated with an increased all-cause and TGCT-specific death.ConclusionsWe report an association between neurodevelopmental disorders and testicular seminoma, and an increased TGCT-specific mortality for TGCT patients with psychiatric disorders.