This Evidence Check review examined the effectiveness of specific behaviour change techniques (BCTs) delivered by telephone in two areas: promoting healthy weight; and supporting parents. The review found that telephone-delivered interventions to promote healthy weight can be effectively used to change physical activity levels and improve diet. Interventions designed to support parents have been shown to improve both children’s behaviour and parents’ wellbeing. None of the included studies identified specific tools to determine which BCTs should be employed and when. The authors recommend the systematic use of theory to identify behavioural determinants and select the most effective BCT.