Background: Chronic fatigue (CF) is more prevalent in Testicular Cancer Survivors (TCSs) 12 years after treatment than in the general population (16% versus 10%). CF-related symptoms of emotional, physical and/or cognitive tiredness may be associated with poor gonadal function (low testosterone (T) and/or high Luteinizing Hormone (LH)). In this longitudinal study we assessed the prevalence of CF median 12 (12y) and 19 years (19y) after treatment in relation to applied treatment, age and levels of T and LH. Methods: T and LH levels were retrieved from 796 TCSs who completed fatigue questionnaires median 12y and 19y after treatment and categorized according to quartile thresholds of healthy controls for decadal age groups. Treatment was categorized as surgery (S, n=162), radiotherapy (RT, n=339) or chemotherapy (CT, n= 295). CF was defined according to previously published cut-off levels. Associations between CF and hormone levels, age and treatment were assessed with logistic regression. Results: CF increased overall significantly from 16% at 12y to 27% at 19y. A total of 67% of those reporting CF at 12y had persistent CF at 19y. The proportion of TCSs with T and/or LH within the poorest quartile increased from 72% at 12y to 81% at 19y. There were no significant associations between CF and T, LH, age or treatment 12 years after therapy. 19y after treatment, CF was significantly associated with the lowest quartile of T (compared to the highest quartile, referent) and previous RT (compared with S, referent) (Odds Ratio 1.9 95%CI: 1.0- 3.5 and 1.7; 95%CI: 1.0- 2.6, respectively). Conclusions: The increase of CF from 12 to 19 years after treatment was remarkable and disturbing. A significant association between CF and RT and the lowest T quartile emerged first almost 20 years after treatment. The increasing proportion of TCSs with CF and decreasing T levels underline the importance of continued long-term assessments of TCSs. T substitution may be considered many years after treatment of TCSs in order to treat CF.