Background: Cisplatin is highly curative treatment for testicular cancer. Most survivors develop azoospermia immediately after cisplatin with recovery expected in 50% at 2 years and 80% at 5 years. Platinum is a heavy metal that can be detected at low levels in serum many years after treatment, however, it is not known whether platinum also persists in semen and if platinum persistence in semen is associated with impaired fertility. Methods: Testicular cancer survivors previously treated with cisplatin were enrolled, relapsed disease treated with salvage chemotherapy was excluded. Semen samples were collected to assess semen quality. Repeat semen collections were performed if azoo- or oligospermia was noted. Serum and semen Platinum levels were determined using HPLC-tandem mass spectrometry. DNA Fragmentation Index (DFI) was measured. Results: From 11/2017 to 12/2019, 38 pts (median age 32 years; range: 19-52; median BSA 2.03; range: 1.81-2.61) were enrolled, 31 were treated with 3 cycles of Bleomycin, Etoposide, Cisplatin. Median cumulative cisplatin dose was 300 mg/m² (range: 274-404). Median serum platinum concentration was 0.1 ng/mL (range: 0-22.6) at a median of 11 months (range 0.5-36) post treatment completion. Median semen platinum concentration was 0.5 ng/mL (range: 0.2-28.7) at a median of 14 months (range: 1.3-40) post treatment completion. Semen platinum levels were higher in semen than in blood drawn at the same time (p = 0.03). Semen platinum levels were associated with time from last cisplatin dosing (r = -0.34; p = 0.09) but not cumulative cisplatin dose (r = -0.10, p = 0.63). Sperm concentration was correlated with time from last cisplatin dosing (r = 0.58, p < 0.001) but not with semen platinum level (r = -0.15, p = 0.46). DFI was associated with time from last cisplatin dosing (r = 0.55, p = 0.08) but not with semen platinum level (r = -0.32, p = 0.33). In 4 pts with serial semen samples available, semen platinum level decreased with time, sperm concentration and motility increased. Conclusions: Platinum can be detected in semen in long-term testicular cancer survivors at higher levels than matched blood samples. Our preliminary findings may have important implications for reproductive health of survivors of advanced testicular cancer, further studies are needed to assess the relationship between platinum persistence in semen and recovery of fertility post chemotherapy.