We report a case of a 37-year-old woman with persistent parvovirus B19 infection and arthralgia mistakenly treated for Lyme disease. This case indicates that poor standardization of both screening and confirmatory assays for Lyme disease can lead to an incorrect diagnosis of Lyme disease. Before making a final diagnosis of Lyme arthritis in an endemic region, other causative agents of arthritis, such as parvovirus B19, should be excluded to avoid unnecessary treatment or to add appropriate therapy in the case of co-infections. Since parvovirus B19 is often associated with arthralgia and can mimic rheumatoid arthritis and autoimmune diseases, it should be included in the differential diagnosis of arthralgia.