Introduction: Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with a wide, various, and sometimes deceptive clinical and serological manifestations. Environmental factors such as ultraviolet radiation, viral infections, drugs, hormones, and chemicals could trigger SLE flares in genetically predisposed patients. Case report: We presented a 13-year-old girl with the first presentation of systemic lupus erythematosus triggered by a mosquito bite. She presented with a malar rash started after a mosquito bite on her left cheek. She had oral ulcers, photosensitivity, lymphopenia, proteinuria, and positive serologic tests for SLE. Renal biopsy revealed class II lupus nephritis. Conclusion: Environmental factors can trigger the onset of SLE in genetically susceptible cases. Besides microbial agents, UV radiation, hormones, drugs, emotional stresses, immunization, and chemicals are some of the published examples. We presented a case with a mosquito bite as the possible environmental trigger.