Autoimmune longitudinal extensive transverse myelitis (LETM) is often combined with connective tissue disorders (CTD). The purpose of this study was to compare the clinical characteristics of autoimmune LETM with and without CTD. Ninety-two patients diagnosed with autoimmune LETM were enrolled from our clinical database and divided into two groups depending on whether they had a concomitant diagnosis of CTD. Differences in clinical, serological, and imaging characteristics between the two groups were evaluated and compared. Fifty-nine LETM patients without CTD and 33 LETM patients with CTD were included. LETM patients with CTD had higher Kurtzke Expanded Disability Status Scale at nadir and more severe sensory dysfunction (p < 0.05) than those without CTD. It was also found that LETM patients with CTD, compared with those without CTD, had elevated levels of immune inflammation markers such as IgG, IgA, and globulins (p < 0.05). These abovementioned characteristics were more prominent in patients with aquaporin-4 antibodies (AQP4-ab) than in those without them. In addition, the most common type of CTD in LETM was Sjögren syndrome (SS), which was usually diagnosed at the time of LETM or later. LETM patients with CTD, especially those with AQP4-ab, had greater sensory dysfunction and higher levels of inflammatory markers than did LETM patients without CTD. Multicenter cooperation and long-term follow-up are necessary to further study the inherent implications and prognosis of the disease.