Schwannomas are rare benign tumors that are often asymptomatic and identified incidentally on imaging studies undertaken for another purpose. Schwannomas arising from the vestibular nerve are the most common site of identification; however, schwannomas can arise extracranially in any peripheral nerve tissue. Here, we present a case study of a patient with a localized rectal adenocarcinoma who was found to have a retroperitoneal schwannoma initially felt to be a lymph node metastasis of his rectal cancer. The diagnosis of schwannoma was confirmed via biopsy, which resulted in changes to the patient's overall management including radiotherapy volumes and recommendation against neoadjuvant or adjuvant systemic therapy.