Subclinical hypothyroidism (SH) is defined as an elevated thyroid stimulating hormone (TSH) in association with a normal total or free thyroxine (T4) or triiodothyronine (T3). It is frequently encountered in both neonatology and general paediatric practice; however, its clinical significance is widely debated. Currently there is no broad consensus on the investigation and treatment of these patients; specifically who to treat and what cut-off level of TSH should be used. This paper reviews the available evidence regarding investigation, treatments and outcomes reported for childhood SH.