Background and Aims: Excessive time and money spent on gambling can result in harms, not only to people experiencing a gambling problem but also to their close family and friends ("concerned significant others"; CSOs). The current study aimed to explore whether, and to what extent, CSOs experience decrements to their wellbeing due to another person's gambling. Methods: We analysed data from The Household Income and Labour Dynamics in Australia Survey (HILDA; N 5 19,064) and the Canadian Quinte Longitudinal Study (QLS; N 5 3,904). Participants either self-identified as CSOs (QLS) or were identified by living in a household with a person classified in the problem gambling category by the PGSI (HILDA). Subjective well-being was measured using the Personal Wellbeing Index and single-item questions on happiness and satisfaction with life. Results: CSOs reported lower subjective wellbeing than non-CSOs across both countries and on all three wellbeing measures. CSO status remained a significant predictor of lower wellbeing after controlling for demographic and socio-economic factors, and own-gambling problems. There were no significant differences across various relationships to the gambler, by gender, or between household and non-household CSOs. Discussion and Conclusions: Gambling-related harms experienced by CSOs was reliably associated with a decrease in wellbeing. This decrement to CSO's wellbeing was not as strong as that experienced by the person with the first-order gambling problem. Nevertheless, wellbeing decrements to CSOs are not limited to those living with a person with gambling problems in the household and thus affect many people.  Kulcsszavak: problem gambling, concerned significant others, gambling harms, subjective wellbeing, HILDA, Quinte Longitudinal Study