Background: Public health policies attempt to increase parental identification of child overweight and obesity. The objective of the present research was to determine the cross-sectional, prospective and longitudinal associations between parental identification of child overweight and child mental health problems. Methods: We made use of two cohort studies of Australian (Longitudinal Study of Australian Children, LSAC) and Irish children (Growing up in Ireland Study, GUI) that measured parental identification of child overweight and child mental health problems. Participant included 6502 (LSAC) and 7503 (GUI) children (49% female) and their parents. Child mental health problems were measured using child, parent and teacher-reported Strengths and Difficulties Questionnaires (SDQ) at ages 9/10 years old to 12/13 years old. In all analyses we controlled for child Z-BMI. Results: In LSAC children whose parents identified them as being overweight at age 10 experienced worse mental health at age 10 ([beta] = 0.21, SE = 0.04) and age 12 ([beta] = 0.13, SE = 0.04) than children whose parents failed to identify them as overweight. In GUI children whose parents identified them as being overweight at age 9 experienced worse mental health at age 9 ([beta] = 0.20, SE = 0.04) and age 13 ([beta] = 0.22, SE = 0.04). In LSAC parental identification of child overweight at age 10 did not significantly predict changes in mental health problems from age 10 to 12 ([beta] = -0.02, SE = 0.03). In GUI parental identification of child overweight was predictive of increases in mental health problems from age 9 to 13 ([beta] = 0.08, SE = 0.03). Conclusions: Parental identification of child overweight and obesity is associated with worse child mental health, independent of child body weight. Parents should be aware of the potential stigma and mental health difficulties associated with labelling a child as overweight.