Abstract Study question Is there a potential for sodium alginate (NaAL) to alleviate the damage induced by BEP chemotherapy in testicular cells and the spermatogenesis process? Summary answer Administering NaAL at doses of 25 and 50 mg/kg demonstrates protective effects against BEP-evoked toxicity damage through the modulation of nitro-oxidative stress, inflammation, and apoptosis. What is known already Testicular tumours are a prevalent malignancy affecting young males aged 20 to 35 years. The globally accepted chemotherapy for testicular cancer involves administering the bleomycin, etoposide, and cisplatin (BEP) regimen in three to four cycles. Unfortunately, the BEP regimen poses a substantial risk of reproductive system toxicity, presenting a significant concern and one of the most challenging long-term complications for young cancer survivors. Sodium alginate (NaAL), an anionic polysaccharide abundant in nature, offers potential solutions with its inherent antioxidant, anti-inflammatory, anti-apoptotic, and anti-proliferative properties. Study design, size, duration Sixty adult male Wistar rats were randomly assigned to six groups (n = 10/group). Groups 1, 3, and 4 received a vehicle, 25 mg/kg, and 50 mg/kg of NaAL, respectively. The remaining groups underwent a three-week cycle of bleomycin, etoposide, and cisplatin (BEP) with or without NaAL. NaAL administration began one week before BEP initiation, continued on days 2, 9, and 16, and extended for one week post the BEP cycle. Participants/materials, setting, methods At the end of the study (day 42), various parameters, including body and testes weight, sperm parameters (count, motility, viability, and morphology), testosterone hormone levels, testicular histopathology, stereological parameters of the testes, and levels of malondialdehyde (MDA), nitric oxide (NO), and total antioxidant capacity (TAC), were assessed. Additionally, the expression of Bcl-2, Bax, caspase-3, p53, and TNF-α was evaluated using real-time PCR and immunohistochemistry. Main results and the role of chance NaAL treatment resulted in a significant improvement in both body weight and testis weight in animals injected with BEP compared to the BEP group (P < 0.05). Stereological procedures, QRT-PCR examination, and immunohistochemical (IHC) staining for quantitative testis analysis indicated that NaAL reversed the impaired spermatogenesis induced by BEP (P < 0.05). Additionally, NaAL restored the disturbance caused by BEP in sperm count, motility, viability, and morphology. The testosterone level significantly decreased in the BEP-treated group compared to the control group (P < 0.05). However, co-administration of 50 mg/kg of NaAL significantly increased the serum testosterone level (P < 0.05). Furthermore, NaAL improved the antioxidant status of the testis by increasing TAC and ameliorating MDA and NO levels. Notably, QRT-PCR examination revealed that NaAL treatment suppressed BEP-induced apoptosis and inflammation by modulating genes such as Bcl-2, Bax, Caspase-3, and p53 in the testis (P < 0.05). Co-administration of 25 and 50 mg/kg of NaAL with the BEP regimen significantly reduced the number of p53 and TNF-α-positive cells compared to the BEP group. Further, NaAL at low and high doses increased the expression of Bcl-2 protein in spermatogenic cells compared to the BEP-treated group. Limitations, reasons for caution Due to limitations in our laboratory resources, we were unable to pursue further studies to validate the mechanism of sodium alginate on specific targets using more advanced techniques such as transfection and transgenic methodologies. Wider implications of the findings These findings illuminate the potential clinical applications of sodium alginate, suggesting its promising role as a beneficial supplement in medical contexts, particularly in addressing fertility issues. Additionally, this antioxidant could accelerate the fertility recovery period in young patients undergoing the BEP chemotherapy regimen, ultimately enhancing their overall quality of life. Trial registration number N/A