Introduction: Acute transverse myelitis is an uncommon inflammatory, intramedullary, disorder of the spinal cord. Spastic paraplegia, impaired sphincter functions, and sensory loss, with sensory level, are the clinical manifestations of this devastating disorder. The utilization of magnetic resonant imaging (MRI) contributes to the surge in the diagnosis of more ATM cases. Although the causes of ATM are numerous, both Mycoplasma pneumoniae and Schistosoma mansoni are uncommon causes and their co-existence in the same patient has not been reported before in Saudi Arabia. Case: We report a 25-year-old ATM male patient presented with a history of sudden onset severe low back pain. Within four hours from the onset of the back pain, he became completely paraplegic with impaired functions of the bowel and urinary bladder sphincter. Furthermore, he lost all modalities of sensory functions in the lower limbs. His examination revealed spastic complete paraplegia with sensory level at T6. Clinical neurological examination revealed normal upper limbs and brain functions. The MRI of the cervico-dorsal spine showed extensive longitudinal hyperintense lesion extending from the upper cervical segments to the lower dorsal segments (extensive longitudinal transverse myelitis). A post-infectious immune-mediated predisposition was highly suspected due to the very high titers of anti-Mycoplasma pneumoniae IgM and IgG that were detected. The immunosuppressant therapy did not improve his paraplegia. A spinal cord biopsy revealed the presence of several Schistosoma mansoni ova surrounded by chronic inflammatory reactions and reactive gliosis. Conclusions: Both Mycoplasma pneumoniae and Schistosoma mansoni should be investigated in cases with extensive longitudinal ATM.