Purpose: To evaluate the efficacy of subcutaneous injection of triamcinolone acetonide (SCTA) in treating upper eyelid retraction and swelling in patients with thyroid eye disease (TED). Patients and Methods: This case series included consecutive patients (aged 16-69 years, monitored from June 2012 to December 2015) with TED-related eyelid symptom and without an enlarged extraocular muscle on magnetic resonance imaging (MRI). SCTA (0.5 mL, 40 mg/mL) was administered to target the orbital fat around the levator palpebrae superioris (LPS) muscle. Patients who did not exhibit improvement after the first trial received an additional injection. Follow-up was conducted for 12 months with 3-month intervals. Eyelid retraction, eyelid swelling, and eyelid lag were evaluated at each follow-up visit. Results: In total, 116 eyelids of 102 patients were analyzed. SCTA led to significant improvement in 93% of eyes (108/116), disappearance of eyelid symptoms (74%, 87%, and 73% in retraction, swelling, and lag, respectively), and improvement of scores (from 1.64 to 0.12, 1.32 to 0.26, and 1.72 to 0.30, respectively). Improvement in eyelid symptoms was observed in eight eyes; however, additional steroid therapy was required in these cases due to the emergence of other extraocular muscle inflammation. Additional injection was required in 39.8% of patients. The clinical activity score was lower in the single SCTA group than in the multiple SCTA group (1.5 vs 0.9; p < 0.01). However, the levels of thyroid-stimulating hormone receptor antibody and MRI findings were not significantly different between the two groups. No elevation in intraocular pressure was observed. Eight female patients experienced menstrual disorder. Conclusion: SCTA effectively reduced LPS muscle enlargement and fat tissue swelling in patients with TED. A single SCTA was sufficient in almost 60% of the patients; nevertheless, follow-up is necessary to detect early signs of orbital inflammation even in eyelid-symptom-improved patients.