The clinical manifestations of systemic lupus erythematosus (SLE) are heterogeneous. Non-specific symptoms such as fever, fatigue, lymph node swelling and loss of weight may precede systemic organ manifestations, making an early diagnosis difficult. Skin manifestations like the classical butterfly rash, as well as involvement of joints, kidneys, the central nervous system, and hematopoiesis are common and characteristic. Helpful laboratory results are an increased ESR, low complement factors such as C4 (hypocomplementemia) and, in particular, antibodies against double-stranded DNA. This article summarizes the clinical manifestations and the most important steps in diagnosing SLE in children and adolescents.