This study was performed to compare the treatment status between older (≥65 years) and younger adults (18-64 years) with severe mental illness (SMI) and explore factors associated with treatment status in rural China. Persons with SMI were identified in one mental health survey in 2015 in 6 townships of Xinjin County, Chengdu, China. Logistic regressions were conducted to explore factors associated with treatment status. Older adults with SMI, especially major depressive disorder, reported significantly lower rates of treatment than younger group. Older age, longer duration of illness, and poor mental status were risk factors for never-treated status in these patients. Never-treated status (46.3%) and poor treatment status in these older patients are serious issues. Different treatment statuses in these patients had various influencing factors. It is crucial to develop culture-specific, community-based mental health services to improve early identification, diagnosis, treatment, and recovery of older adults with SMI in rural China.