Third Culture Kids (TCK) are generally considered to be children who spend a significant period living outside of their home country but reside only temporarily in one or more host country/ies. TCKs' upbringing, it is argued, may lead to a number of negative psychological outcomes including depression, anxiety, and identity and attachment issues. This quantitative study based on a total of 489 participants compares the self-report responses of adults who had been TCKs with those of non-TCK adults, on the measures of ethnic identity, wellbeing, loneliness, attachment, resilience, and self-concept clarity. Results indicate that TCK adults had a weaker ethnic identity, greater resilience, and were less comfortable forming close relationships than non-TCK adults. Among TCK adults, having siblings was associated with reduced attachment anxiety and greater resilience, while practising a religion was related to increased ethnic identity. Findings indicate the need to raise awareness among parents, teachers, and counsellors about the difficulties that TCKs might face.