The shared family environment is an important risk factor in the development of childhood obesity. This study aims to examine differences in maternal psychopathology, family functioning, expressed emotion and coping skills between families of a child with obesity and those with a normal‐weight child. This case–control study consisted of 50 mothers with a child (age 8–12 years) with obesity (p ≥ 97) and a control group of 50 mothers of a child with normal weight (p < 85), matched for age, sex and socio‐economic status. Compared with families with normal‐weight children, those with children with obesity showed significant differences in levels of trait anxiety, criticism and over‐protectiveness, and maladaptive coping skills. Structural equation modelling revealed that the mothers' psychopathology predicted children's body mass index (BMI) z‐scores through expressed emotion and maladaptive coping scores. There were significant direct and indirect relations among maternal BMI, psychopathology, expressed emotion and coping, which all together explained 26.5% of variance of children's BMI z‐scores. Considering this relation between maternal variables and child weight status, childhood obesity intervention programs may benefit from targeting maternal BMI, psychopathology, expressed emotion and coping skills. Copyright © 2017 John Wiley & Sons, Ltd and Eating Disorders Association.