It is important to find and identify more biological adsorbents that can effectively remove metals from water instead of using the traditional approach. In the present study, a fungal strain resistant to cadmium was isolated from polluted sites. It was identified morphologically and molecularly as Alternaria tenussemia, with an accession number of OQ691600. Heat-inactivated biomass of A. tenussemia was evaluated for cadmium (Cd) biosorption. The biosorption process was conducted at a temperature of 28±2°C to remove Cd from water at an initial concentration of 92 mg/ L, under different conditions, such as pH (4–6), biosorbent dose (1–3 g/L), and sorption time (15–60 min). The obtained results demonstrated that the dead biomass of A. tenussemia effectively removed Cd, with maximum significant biosorption efficiency of 99.95±0.003% and capacity of 92.33±0.21 mg/g, which were achieved at a pH value of 6 for 30 min and a biosorbent dose of 1 g/L. Fourier transform-infrared (FT-IR) spectroscopy analysis revealed changes in the functional groups present on the surface of A. tenussemia biomass through the biosorption process. Following the biosorption process, three groups of male albino rats were used. The negative control group received only double-distilled water through oral administration. The Cd-polluted water group received a Cd aqueous solution (92 mg/L) through oral administration for 30 days. The treatment group received Cd aqueous solution (92 mg/L) through oral administration after treatment with A. tenuissima as the biosorbent material for a period of 30 days. The results showed that Cd caused a significant drop in weight gain and testicular index weight, as well as total protein, albumin, semen count, and motility. There were significant increases in abnormal sperm, the spleen, and brain index weight, as well as biochemical parameters, including aspartate aminotransferase, alanine aminotransferase, urea, creatinine, and uric acid, showed notable changes. The liver, kidney, testis, and epididymis of male albino rats showed several histopathological changes along with bioaccumulation of Cd traces in liver and kidney tissues. However, in the treatment group, all these findings were noticeably improved. Based on our findings, the dead biomass of A. tenuissima has the potential to be a very effective biosorbent for removing cadmium from water, without causing any hazardous effects on animals.