Paraneoplastic syndromes are rare but possible manifestations of colorectal cancer. We present THE CASE of a 51-year-old female diagnosed with cT3N2 rectal adenocarcinoma who developed back pain and progressive muscle weakness during preoperative treatment. She had a rapid worsening in mobility and was ultimately ambulating with a wheelchair, despite physical therapy and conservative treatments. Extensive laboratory workup including onconeural antibodies was negative and her lower extremity electromyogram was suggestive of a subacute demyelinating lumbosacral plexopathy. After multidisciplinary discussion, the decision was made to proceed with curative resection. She had significant improvement in her weakness following resection, suggesting a paraneoplastic etiology. One year after resection, she remains free of disease and is ambulating comfortably. Onconeural antibodies can be a helpful diagnostic tool, but their absence does not rule out paraneoplastic disease. A high index of suspicion is necessary when assessing patients with atypical symptoms, particularly with the rise of colorectal cancer in young adults.