Granulocyte colony-stimulating factor (G-CSF) is commonly used with neutropenic patients to accelerate recovery. G-CSF is a hematopoietic cytokine that regulates the proliferation and differentiation of neutrophil precursors, and is known as a safe and effective treatment for chemotherapy-induced neutropenia. However, we encountered a case in which a patient with systemic lupus erythematosus (SLE) developed mesenteric vasculitis after G-CSF administration. The patient was a 36-year-old female admitted with fever, arthralgia, and generalized erythematous rash. Despite symptomatic improvement with a high-dose steroid, severe neutropenia persisted for three weeks, precipitating a decision to use G-CSF to enhance recovery. Mesenteric vasculitis developed 15 hours after administration of G-CSF injection. Because the response of immune cells such as neutrophils and T cells is uncontrolled and dysfunctional in patients with lupus, G-CSF therapy should be used with caution.