Concerned significant others (CSOs) are people who have been negatively affected by another person’s gambling. This study estimated the national prevalence of CSOs in Australia and identified their characteristics. It also compared the types and number of harms experienced by CSOs based on their relationship to the person who gambles and their gender. Data were drawn from a national telephone survey and included 11,560 adults. Around 6% of the participants were CSOs. Emotional harms were the most common type of harm. This was followed by relationship, financial, health, and work/study harms, respectively. CSOs reported the most harm from a former partner, followed by current partner, other family members, and non-family members. Women reported more harm and were more likely to report harm from a family members’ gambling. Men were more likely to report harm from a non-family member’s gambling.
