Necrotic decayed primary molars with necrotic pulp tissues may show periapical involvement and root resorption. In this case report, a pediatric patient with a very common chief complain and clinical picture of necrotic badly decayed molar, introduced a very interesting case when radiographic investigation was performed, which showed that root resorption of the adjacent healthy molar occurred. The current report is, to the best of our knowledge, the first to report such finding in primary dentition.