Background: The objective of this study was to describe and quantify mental health (MH) admissions experienced by patients with unintentional burns subsequent to their injury. Methods: A retrospective population-based cohort study that used de-identified linked hospital, death and mental health in-patient case registry data of all burn patients hospitalised for unintentional burns (n = 10,460) between 2000 and 2012 in Western Australia and an age and gender matched uninjured comparison cohort (n = 42,856). Cohorts had a median age at study index of 26 years with males comprising 66% of each cohort. MH admissions for 5 years before and after the injury were examined. Negative binomial and Cox proportional hazards regressions were adjusted for socio-demographic and pre-existing health conditions and used to quantify associations between burns and MH hospitalisations. Results: In the burn cohort during the 5-year post-burn period, 4% had a MH admission, 2% were admitted for self-harm, and 3% were admitted for a behavioural disorder caused by drugs/alcohol. Significantly elevated adjusted admission rates for MH conditions were observed for the burn cohort compared with the uninjured cohort (IRR, 95% CI: 4.89, 3.52–6.79). Increased MH admission rates were found for all age groups but were most pronounced in those younger than 18 years of age at time of burn (IRR, 95% CI: 6.28, 3.00–13.14), followed by those aged 18–60 (5.14, 3.59–7.35) and those over 60 years (IRR, 95% CI: 2.97, 1.38–6.39) compared to the uninjured cohort. Gender-specific analyses showed significant differences for male (IRR, 95% CI: 4.48, 3.05–6.59) and female burn patients (IRR, 95% CI: 6.00, 3.62–9.92), compared to uninjured. The burn cohort had higher adjusted first time admissions for MH conditions (HR, 95% CI: 3.55, 2.72–4.64), mood and anxiety disorders (HR, 95% CI: 3.77, 2.81–5.08), psychotic disorders (HR, 95% CI: 3.55, 1.99–6.15) and behavioural disorders related to alcohol/drugs (HR, 95% CI: 4.75, 3.09–7.28) for five years after the initial burn. Conclusions: Patients hospitalised for unintentional burns had significantly higher MH admission rates after discharge than that observed for an uninjured cohort. Ongoing mental health support is clearly indicated for many burns patients for a prolonged period after discharge.