Research on the impact of the keyworker‐child relationship on residential staff is scarce. This longitudinal study investigated the potential moderating effects of child and keyworker attachment styles on the link between child behavioural problems and staff burnout and the moderating effects of child attachment style on the link between keyworker attachment style and keyworker burnout. Participants included 261 children and 59 residential child care workers, from 5 orphanages in Saudi Arabia. Five self‐report measures were utilised: The Strengths and Difficulties Questionnaire, the Security Scale, the Coping Strategies Questionnaire, the Maslach Burnout Inventory and the Experiences in Close Relationships Questionnaire. Keyworkers caring for relatively non‐avoidant children and those with an avoidant attachment style themselves experienced relatively high burnout a year later. Relatively high burnout was also reported by avoidant keyworkers who cared for avoidant and generally insecure children, while anxiously attached keyworkers reported relatively high burnout when they cared for children with any type of insecure attachment style. The present findings highlight essential interpersonal processes involved in the development of burnout in residential child care workers and call for the employment of attachment‐focused interventions as measures of burnout prevention.