Background and objectives: This study was conducted to determine and explain the relationship between the loneliness perceptions and well‐being of family caregivers of psychiatric patients. Methods: This cross‐sectional and descriptive study was conducted with the families of 141 individuals with mental illness, who were outpatients psychiatry clinic of a university hospital. Findings: There was a statistically significant moderate relationship between loneliness levels and well‐being subscales of the psychiatric patients' caregivers (p < 0.001). Practical implications: Mental health nurses should carefully evaluate the perception of loneliness of family caregivers when diagnosing the family and determining needs.