Tracking populations through increasingly frequent climate disasters and understanding what contributes to mental health risks is crucial for adaption and planning for a climate changed world. We aimed to examine mental health trajectories after consecutive climate-related disasters and assess differences in mental health outcomes by temporal proximity to previous disasters and risk profiles. Using longitudinal population-based Australian data from 2009 to 2019, people who experienced home damage from at least one disaster (flood, bushfire, or cyclone) were included in the exposure population and tracked from pre-disaster to post-disaster years after each exposure. Cumulative mental health effects of each sequential exposure were estimated through various mental health measures using a panel event study design with linear models in comparison to unexposed matched controls, pre-disaster baselines, and across stratified risk groups. The main mental health outcome was measured with the 5-item mental health inventory (MHI-5). Mental health effects became more severe with successive disasters. MHI-5 scores declined by 1·61 (95% CI -2·69 to -0·52) and 3·37 (-6·45 to -0·29) during the first and repeat disaster exposures, respectively, compared with the year preceding the first disaster. Recovery to a pre-disaster baseline was more delayed with repeat disaster exposures. There were greater declines in mental health when disasters were closer to the previous exposure (1-2 years apart) than further away (3 or more years). Risk factors that shape mental health trajectories either remained consistent across multiple exposures (social support as protective and long-term health conditions as risks) or became more salient during subsequent exposures (lower household income and rural areas more vulnerable to the mental health effects of repeat disasters). Additional disaster exposures were associated with greater declines in mental health and shifts in some risk factors. Multiple disaster exposures must be urgently considered in public health, welfare, and disaster services. Australian Research Council.