Emotional availability (EA) characterizes a warm, close relationship between caregiver and child. We compared patterns (clusters) of EA on risk factors, including those for borderline personality disorder (BPD). We sampled 70 children aged 4 to 7 years from low socio‐economic backgrounds: 51% of whose mothers had BPD. We coded filmed interactions for EA: mothers' sensitivity, structuring, non‐intrusiveness, non‐hostility, and children's responsiveness to, and involvement of, mothers. We additionally coded children's over‐responsiveness and over‐involvement. Using person‐centred analyses, we identified four clusters: high functioning, low functioning, asynchronous (mothers above average on two of four dimensions and children below), and below average. Mothers in the low‐functioning cluster had lower income, less social support, more of the borderline feature of negative relationships, and more depression than did mothers in the high‐functioning cluster. The children in the low‐functioning group had more risk factors for BPD (physical abuse, neglect, and separation from, or loss of caregivers, and negative narrative representations of the mother–child relationship in their stories) than did children in the high‐functioning group. The asynchronous group included older girls who were over‐responsive and over‐involving with their mothers in an apparent role reversal. Interventions targeting emotional availability may provide a buffer for children facing cumulative risks and help prevent psychopathology. Highlights This paper investigated how mother‐child emotional availability (warmth and closeness) relates to risk factors for borderline personality disorder, including mother‐child role reversal. In filmed mother‐child interactions, low emotional availability was associated with risk for borderline personality disorder and role reversal was more likely for older girls. Findings support the cumulative risk hypothesis and may inform interventions to improve mother‐child emotional availability to prevent the development of psychopathology.