This study aimed to examine the impact of community mental health (CMH) care following index hospital-treated intentional self-harm (ISH) on all-cause mortality. A secondary aim was to describe patterns of CMH care surrounding index hospital-treated ISH. A longitudinal whole-of-population record linkage study was conducted (2014-2019), with index ISH hospitalization (Emergency Department and/or hospital admissions) linked to all available hospital, deaths/cause of death, and CMH data. Australia's most populous state, New South Wales (NSW) comprised approximately 7.7 million people during the study period. CMH services are provided statewide, to assess and treat non-admitted patients, including post-discharge review. Individuals with an index hospital presentation in NSW of ISH during the study period, aged 45 years or older. CMH care within 14 days from index, versus not. Cox-proportionate hazards regression analysis evaluated all-cause mortality risk, adjusted for relevant covariates. Totally, 24,544 persons aged 45 years or older experienced a nonfatal hospital-treated ISH diagnosis between 2014 and 2019. CMH care was received by 56% within 14 days from index. Survival analysis demonstrated this was associated with 34% lower risk of death, adjusted for age, sex, marital status, index diagnosis, and 14-day hospital readmission (HR 0.66, 95% CI 0.58, 0.74, p < 0.001). Older males and chronic injury conveyed significantly greater risk of death overall. CMH care within 14 days of index presentation for self-harm may reduce the risk of all-cause mortality. Greater effort is needed to engage older males presenting for self-harm in ongoing community mental health care.