["Journal of Intellectual Disability Research, EarlyView. ", "\nABSTRACT\n\nBackground\nThe closeness of the parent–child relationship may be a crucial factor in the development of all children, including those with intellectual disabilities. Previous research has suggested that there may be subgroup trajectories of mother–child closeness in families of children with intellectual disabilities during childhood. Our aim was to examine whether potential subgroup trajectories of mother–child closeness in families of children with intellectual disabilities exist and what factors influence identified trajectories.\n\n\nMethods\nData from 353 maternal primary caregivers who took part in three waves of the 1000 Families Study, over the course of 8 years, were analysed using growth mixture modelling. Mother–child closeness was measured using the Child Parent Relationship Scale at all three waves. Time‐varying (maternal psychological distress, child behaviour and emotional problems, child prosocial behaviour) and time‐invariant (child's level of communication skills, autism diagnosis) correlates of class membership and within‐class trajectories were included in the analysis.\n\n\nResults\nThe findings suggested a single trajectory of mother–child closeness, with observed heterogeneity accounted for by the covariates. Mother–child closeness on average remained consistent over time. Maternal psychological distress and an autism diagnosis were generally associated with reduced levels of mother–child closeness. The child's level of communication skills and child prosocial behaviour were associated with increased levels of closeness over time. Child behaviour and emotional problems were not associated with mother–child closeness.\n\n\nConclusion\nFurther research using larger longitudinal population datasets is needed to explore whether there may be distinct trajectories of mother–child closeness in families of children with intellectual disabilities. The current findings suggest that supports for mother–child relationships might be targeted in families of children with lower levels of communication or prosocial behaviour skills, an additional autism diagnosis and when mothers are experiencing higher levels of psychological distress.\n\n"]