There is no single diagnostic test for any rheumatic disease. The diagnosis of a rheumatic disease is made by the sum of the findings in history, physical examination, laboratory, and imaging tests. A differential diagnosis list in pediatric rheumatology is quite long and mainly includes malignant, infectious, and inherited metabolic disorders. We aim to present cases that were referred to a pediatric rheumatology outpatient clinic with provisional diagnosis of a rheumatic disease but finally diagnosed with a non-rheumatic disease in order to emphasize the importance of differential diagnoses. Eight cases were presented in this manuscript. Five cases were referred with the provisional diagnosis of juvenile idiopathic arthritis. Sarcoidosis, chronic non-bacterial osteomyelitis, and autoinflammatory disease were the provisional referral diagnoses in three patients. Definitive diagnoses of the patients were as follows: acute lymphoblastic leukemia (two cases), bilineage acute leukemia, Hodgkin lymphoma, brucellosis, mucolipidosis type III, anhidrotic ectodermal dysplasia, and Freiberg disease. In children presenting with rheumatic complaints malignant, infectious and inherited metabolic disorders should always be in the differential diagnosis list of a pediatric rheumatologist. Alternative diagnoses should always be considered even in patients with a rheumatic disease when the patient does not respond to treatment or follows an unusual clinical course.