Affiliated stigma often refers to internalized stigma among family members of stigmatized individuals. This study aimed to investigate the relationship between affiliate stigma and quality of life (QOL) among primary caregivers of individuals with mental illness undergoing treatment at the Institute of Mental Health, Singapore. Three hundred and fifty caregivers were recruited for the study. The World Health Organization Quality of Life questionnaire (WHOQOL-BREF) and Family Stigma Scale (FSS) were administered to the primary caregivers of patients with mental illness. Multiple linear regression analyses were conducted to investigate the association of affiliate stigma with QOL. A high proportion of caregivers of individuals with mental illness experience affiliate stigma in Singapore. All four QOL domains were significantly associated with affiliate stigma. These findings entail that it is imperative to improve public's perception of those with mental illness to reduce stigmatization and thus improve caregiver's QOL.