Obesity is associated with better outcomes in some metastatic cancers, for example, renal cancer, but the association between BMI and germ cell tumour (GCT) outcomes has not been reported. Medical records of 1,161 patients with GCT who were treated at Dana–Farber Cancer Institute between 1997 and 2012 were reviewed and logistic regression analysis used to investigate the association between BMI and clinical features of GCT. In men with stage 1 GCT, BMI ≥25 was not associated with an increased risk of relapse compared with those with BMI <25. In metastatic disease, men with BMI <25 were less likely to present with good-risk disease, but BMI was not associated with risk of relapse. Overall, men with lower BMI are more likely to present with intermediate-risk or poor-risk GCT.