OBJECTIVE To assess the incidence and severity of 12 systemic side effects of serial intralesional steroid injections (SILSI) in patients with idiopathic subglottic stenosis (iSGS). METHODS This retrospective study included patients with iSGS who underwent SILSI with Triamcinolone 40 mg/dL. After SILSI, the patients were asked to answer 12 questions regarding frequently encountered systemic side effects of steroids. Each answer was rated as mild, moderate, or severe. Descriptive statistics were used to analyze and present the findings. RESULTS The study included 49 patients (42 female and 7 male) with a mean age of 59.1 years (range 21-83 years). Post-SILSI treatment, 27 (55%) reported experiencing side effects while 22 (45%) patients reported no side effects. The most frequent side effect reported in women of reproductive age (n: 8) was menstrual irregularities (3/8, 37%). Other frequently reported side effects were feeling joyful and sleeping difficulties, each reported by 30% of the patients. All side effects resolved after the completion of SILSI. CONCLUSIONS SILSI can be administered with minimal tolerable side effects. Clinicians should make their patients aware of the most frequent side effects. Special attention should be given to women of reproductive age to inform them of the possibility of menstrual irregularities during SILSI.