Childhood obesity is a growing problem with a complex aetiology, for which multidisciplinary interventions are required. Our programme describes a novel structured psychosocial family‐based intervention targeting the emotional regulation in childhood obesity, using a train trip metaphor aimed at improving healthy lifestyles for the family. The aims were (a) to describe the feasibility and acceptability of this psychosocial family‐based intervention among children with overweight or obesity in primary care and (b) to examine the effectiveness of the “ENTREN‐F” programme (with family intervention) compared with the “ENTREN” programme (without family intervention) among Spanish children regarding anthropometric variables, physical activity, emotional well‐being, and family functioning. Children were randomly allocated to either ENTREN‐F programme (n = 30) or psychological intervention for children (ENTREN, n = 40), and assessments were carried out over time (T0 baseline vs. T1 post/6‐month vs. T2 6‐month follow‐up). Both parent groups expressed high levels of satisfaction with the interventions. ENTREN‐F resulted in higher adherence to treatment and was more effective in improving z–body mass index, reducing children’s anxiety, and increasing family adaptability than the ENTREN programme. There were no significant changes in parents’ emotional well‐being and expressed emotion. Both groups improved in the children’s emotional well‐being and light physical activity. In summary, this multidisciplinary psychosocial family‐based intervention was succesful.