Nation-wide research on mental health problems amongst men and women during the transition from employment to retirement is limited. This study sought to explore the relationship between retirement and mental health across older adulthood, whilst considering age and known risk factors for mental disorders. Data were from the 1997 National Survey of Mental Health and Well-being, a cross-sectional survey of 10,641 Australian adults. The prevalence of depression and anxiety disorders was analysed in the sub-sample of men (n = 1928) and women (n = 2261) aged 45-74 years. Mental health was assessed using the Composite International Diagnostic Instrument. Additional measures were used to assess respondents' physical health, demographic and personal characteristics. The prevalence of common mental disorders diminished across increasing age groups of men and women. Women aged 55-59, 65-69, and 70-74 had significantly lower rates of mental disorders than those aged 45-49. In contrast, only men aged 65-69 and 70-74 demonstrated significantly lower prevalence compared with men aged 45-49. Amongst younger men, retirees were significantly more likely to have a common mental disorder relative to men still in the labour force; however, this was not the case for retired men of, or nearing, the traditional retirement age of 65. Men and women with poor physical health were also more likely to have a diagnosable mental disorder. The findings of this study indicate that, for men, the relationship between retirement and mental health varies with age. The poorer mental health of men who retire early is not explained by usual risk factors. Given current policy changes in many countries to curtail early retirement, these findings highlight the need to consider mental health, and its influencing factors, when encouraging continued employment amongst older adults.