Background: Survivors of testicular germ cell tumors (GCT) may suffer from long-term cognitive impairment. We hypothesized that disruption of intestinal barrier during chemotherapy and/or radiotherapy may be a contributing factor of cognitive dysfunction within the gut-blood-brain axis. Methods: GCT survivors (N = 142) from National Cancer Institute of Slovakia completed the Functional Assessment of Cancer Therapy Cognitive Function questionnaires during their annual follow-up visit at 9-year median (range 4-32). Biomarkers of gut microbial transfer and dysbiosis (GMT) high mobility group box-1 (HMGB-1), lipopolysaccharide (LPS), d-lactate and sCD14 were measured from peripheral blood obtained during the same visit. Each questionnaire score was correlated with biomarkers of GMT. Survivors were treated with orchiectomy only (N = 17), cisplatin-based chemotherapy (N = 108), radiotherapy to the retroperitoneum (N = 11) or both (N = 6). Results: GCT survivors with higher sCD14 had worse cognitive function perceived by others (CogOth domain) (mean ± SEM; 14.6 ± 0.25 vs 15.4 ± 0.25, p = 0.019), lower perceived cognitive abilities (CogPCA domain) (20.0 ± 0.74 vs 23.4 ± 0.73, p = 0.025) and lower overal cognitive function score (109.2 ± 0.74 vs 116.7 ± 1.90, p = 0.021). There were no significant cognitive declines associated with HMGB-1, d-lactate and LPS. Survivors treated with ≥ 400mg/m2 of cisplatin based chemotherapy had higher LPS (567.8 ± 42.7 vs 462.9 ± 51.9, P = 0.03). Survivors treated with chemotherapy + radiotherapy vs orchiectomy only had non-significantly higher sCD14 (7279.9 ± 810.1 vs 5851.0 ± 481.7, P = 0.09). Conclusions: sCD14 may serve as a promising biomarker of cognitive impairment in long-term cancer survivors. While chemotherapy and radiotherapy-induced intestinal injury may be the underlying mechanism, further research using animal models and larger patient cohorts are needed to explore the pathogenesis of cognitive impairment in GCT survivors.