It has been demonstrated that obsessive-compulsive disease and/or tic syndromes in children may be triggered by an antecedent infection especially with group A beta-hemolytic streptococci, and this subgroup of children has been designated by the acronym PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections). Other infectious agents such as viruses and bacteria have also been reported to be associated with the acute onset or dramatic exacerbation of obsessive-compulsive disease or Tourette syndrome, and another acronym, PITAND (pediatric infection-triggered autoimmune neuropsychiatric disorder) has appeared in the literature. The involvement of other infectious agents such as Mycoplasma pneumoniae has been described in single case reports. We describe a case of a 5.5-year-old boy who suddenly developed obsessive-compulsive disease symptoms during a M. pneumoniae pneumonia. After treatment with oral clarithromycin, all his obsessive-compulsive disease symptoms disappeared. To our knowledge, this is the first report that shows the association between Mycoplasma pneumoniae infection and obsessive-compulsive disease.