Spinal dumbbell-shaped schwannomas (SDS) are often difficult to resect completely and safely because of their anatomical characteristics. As a result, there is no clear consensus regarding the optimal surgical strategy or postoperative management. Previous studies have reported that postoperative pathological findings, such as the Ki-67 labeling index, and residual tumor margins on postoperative MRI are associated with tumor recurrence or regrowth. However, these factors can only be evaluated after surgery, and the relationship between preoperative clinical data and postoperative tumor regrowth has not been fully clarified. This study aimed to evaluate preoperative clinical and imaging data in patients with SDS and to identify risk factors for postoperative tumor regrowth. We retrospectively reviewed 20 patients who underwent surgery for SDS at our institution between January 2013 and March 2023 and had at least two postoperative MRI evaluations. The standard surgical approach at our institution is a single-stage posterior surgery with maximal safe resection, without aiming for total resection. Clinical data, preoperative and postoperative MRI findings, reoperations, and complications were analyzed. Tumor growth was defined as the difference in maximum residual tumor diameter between the first and second postoperative MRI examinations. Patients were divided into an enlargement group (tumor growth ≥2 mm) and a non-enlargement group (<2 mm). Twelve patients were classified into the enlargement group and eight into the non-enlargement group. Patients whose preoperative MRI showed a homogeneously high signal on T2-weighted images did not demonstrate postoperative tumor regrowth, and this difference was statistically significant (p = 0.012). Furthermore, the mean tumor growth rate was significantly higher in patients without homogeneously high T2 signal compared with those with homogeneously high T2 signal (p = 0.008). The mean growth rate in the non– T2-high group exceeded 3 mm per year, suggesting a potential increased risk for reoperation. These findings indicate that preoperative MRI signal characteristics, particularly T2-weighted signal patterns, may help predict postoperative tumor regrowth in patients with SDS. Preoperative MRI-based risk stratification may be useful for optimizing surgical planning and tailoring postoperative follow-up strategies.