Poor mental health is strongly associated with disability acquisition. Social capital and healthier lifestyles pre-disability onset may help promote mental health resilience (i.e. a state of seemingly being unaffected by the event), or the capacity to ‘bounce back’, post-acquisition. This paper used a novel methodology (discrete trajectory mixture models) to examine discrete trajectories in mental health before and after disability acquisition in the Household Income Labour Dynamics in Australia (HILDA) survey. Group membership in association with pre-onset social capital and healthy lifestyles were then examined using multinomial logistic regressions. Four discrete trajectory groups were identified in 2904 Australians reporting onset of ongoing disability, with about 28.4% demonstrating mental health resilience. Three other groups were identified, each demonstrating increasingly severe reductions in mental health. No clear ‘bounce back’ group was observed. Group membership was associated with participants who felt they had ‘no-help from others’ prior to disability acquisition. Pre-disability acquisition measures of social capital and unhealthy behaviours moderated the association between disability acquisition and mental health trajectories. Social capital was protective only for the respondents who had poorer mental health before disability onset and had less resilience after onset, and long working hours and less resilience were positively associated. Public policies that help to enhance levels of social capital and reduce unhealthy behaviours at a population level may help to promote mental health resilience to adversities such as the acquisition of disability.