Convincing clinical evidence exists to support early surgical decompression in the setting of cervical spinal cord injury (SCI). However, clinical evidence on the effect of early surgery in patients with thoracic and thoracolumbar (from T1 to L1 [T1-L1]) SCI is lacking and a critical knowledge gap remains. This randomized controlled trial (RCT) sought to evaluate the safety and efficacy of early (<24 h) compared with late (24-72 h) decompressive surgery after T1-L1 SCI. From 2010 to 2018, patients (≥16 years of age) with acute T1-L1 SCI presenting to a single trauma center were randomized to receive either early (<24 h) or late (24-72 h) surgical decompression. The primary outcome was an ordinal change in American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade at 12-month follow-up. Secondary outcomes included complications and change in ASIA motor score (AMS) at 12 months. Outcome assessors were blinded to treatment assignment. Of 73 individuals whose treatment followed the study protocol, 37 received early surgery and 36 underwent late surgery. The mean age was 29.74 ± 11.4 years. In the early group 45.9% of patients and in the late group 33.3% of patients had a ≥1-grade improvement in AIS (odds ratio [OR] 1.70, 95% confidence interval [CI]: 0.66-4.39, p = 0.271); significantly more patients in the early (24.3%) than late (5.6%) surgery group had a ≥2-grade improvement in AIS (OR 5.46, 95% CI: 1.09-27.38, p = 0.025). There was no statistically significant difference in the secondary outcome measures. Surgical decompression within 24 h of acute traumatic T1-L1 SCI is safe and is associated with improved neurological outcome, defined as at least a 2-grade improvement in AIS at 12 months.