Background It is generally agreed that the ideal time for treating Class II malocclusions is adolescence, when the patient is approaching the pubertal growth spurt. Nevertheless, it has been reported in the literature that in the presence of what has been defined as a "socially debilitating" Class II malocclusion, characterised by severe overjet and mandibular retrognathism, a first phase of treatment should be provided already in the early mixed dentition phase, for the benefit of a positive psychologic effect. Such early treatment should first involve correction of the transverse dimension of the maxilla, to enable spontaneous forward movement of the mandible or mandibular advancement by functional appliances. Case report This case report describes the early treatment of a severe Class II malocclusion, with major overjet and mandibular retrognathism. Treatment involved rapid maxillary expansion, followed by the use of the Forsus Fatigue Resistant Device (FRD; 3M Unitek, Monrovia, CA, USA) as a fixed functional appliance. Orthodontic records were taken before and after the early phase of treatment. Cephalograms and digital models were superimposed to evaluate the produced dento-alveolar and skeletal changes. The early phase of treatment was found to be effective at reducing the sagittal jaw discrepancy, controlling the patient unfavourable growth pattern, and improving the child aesthetics.