Objective This present study estimated the psychiatric morbidity among informal caregivers of older adults and investigated its association with their socio-demographic factors and older adult's health status, including dementia, depression and physical health conditions. Methods Data from a national cross-sectional survey were used. For each participating older adult, an informal caregiver who 'knew the older adult best' and was aware of their health condition, was also interviewed to collect information on the older adults' care needs, and behavioral and psychological symptoms of dementia (BPSD). Data from 693 pairs was used. Informal caregivers were administered the Self Reporting Questionnaire (SRQ)-20 and psychiatric morbidity was defined as those with a total SRQ score of ≥ 8. Measures included informal caregivers' socio-demographic characteristics, assessment of dementia and depression in the older adults and self-report on their lifetime and current physical conditions. The association of socio-demographic characteristics, health conditions, care assistance and BPSD was investigated using backward stepwise logistic regression analysis where psychiatric morbidity (total SRQ score < or ≥ 8) was used as a dependent variable and all other variables served as independent covariates. Results Among informal caregivers, 8.8% exhibited psychiatric morbidity. Higher proportions of spousal caregivers and caregivers of older adults having more care needs and BPSD exhibited psychiatric morbidity. After adjusting for all covariates, caregivers' marital status, and the presence of BPSD and dementia in the older adults were identified as the strongest correlates of caregivers' psychiatric morbidity. The prevalence of psychiatric morbidity was 10%, 13.9% and 12.7% respectively in these groups. Married caregivers had higher odds of psychiatric morbidity (OR 2.50, 95% CI: 1.13-5.52). In addition, caregivers of older adults' with any BPSD (OR 5.87, 95% CI: 2.60-13.24) and dementia (OR 2.28, 95% CI: 1.23-4.20) were also associated with higher odds of psychiatric morbidity. Conclusion Informal caregivers' marital status and presence of any BPSD and dementia in the older adults in their care were identified as the strongest correlates of caregivers' psychiatric morbidity. Clinicians should be cognizant of the risk in this group of caregivers and assess and intervene to alleviate caregivers' psychological problems.