Moon-like facies (MLF) are a typical side effect of glucocorticoid (GC) therapy; however, its predisposing factors, relationship with GC-induced complications, and effects on body image are not well understood. This study aimed to determine the predisposing factors for MLF during GC therapy; its association with GC-induced diabetes, hypertension, and dyslipidemia; and its effects on body image. This prospective observational study spanned 24 weeks and targeted patients who received GC therapy at the University of Yamanashi Hospital from June 2020 to August 2022. The MLF was defined based on the following 3 factors: (1) an increase in facial measurement lengths, (2) subjective facial changes by patients' self-assessment using a visual analog scale; (3) objective and qualitative facial changes assessed by physicians. We examined the predisposing factors for MLF and the association of MLF with GC-induced diabetes, hypertension, dyslipidemia, and body image. The cumulative incidence rate of MLF at 24 weeks was 37.6%. Predisposing factors for MLF were an initial oral prednisolone dosage of ≥ 30 mg/day [odds ratio (OR) 63.91, 95% confidence interval (CI) 5.82-701.81] and female (OR 6.66, 95% CI 1.35-32.79). MLF showed a significant association with the onset of GC-induced diabetes (OR 6.58, 95% CI 1.25-34.74). MLF was also an independent factor contributing to body image disturbance (β = -18.94, P = .01). MLF contributes to body image disturbance and is associated with the development of GC-induced diabetes; therefore, it is clinically important as a physical manifestation of GC therapy.