The term infraclusion is usually used to define mandibular primary teeth in posterior region that remain below the occlusion level. The degree of infraclusion depends on some factors like deviation below the occlusal plane, and infraclusion of tooth in the alveolar bone. Deficient eruptive force, disturbed metabolism of the periodontal ligament, trauma, local inflammation, deficient local vertical bone growth, disturbance in interaction between normal resorption and hard tissue repair, ankylosis and hereditary components have been given as etiological factors. Complications of infraclused primary molars are tipping of the neighboring teeth, space loss, supraeruption of the antagonists, and dislocations of permanent teeth lying under the primary tooth. In this case report, after reviewing the literature a patient with infraclused mandibular primary second molar has been examined to observe the complications of infraclusion. With an appropriate treatment approach, a proper condition was prepared for the eruption of permanent teeth.