Objective: This study projects midlife obesity status in future older Australians. Design and Methods: Cross-sectional prevalence of being obese or overweight by broad age groups was interpolated to obtain single-year-age data. These estimates were then used to derive prevalence of normal weight and underweight. Data by birth year and year of observation of persons aged 30–70 years were used to construct prediction equations. Results: Results show that older people with a history of midlife obesity is projected to rise substantially in the future. For people aged 65 years, midlife obesity was estimated at 22% in 2010 and is projected to increase to 43% for males and 37% for females in 2050. Conclusion: While the proportion of individuals with midlife normal weight is projected to decline substantially, prevalence of midlife overweight remains almost stable. The number of persons aged 65 years and over having a history of midlife obesity is projected to increase nearly six-fold from less than 500,000 persons in 2010 to 2.8 million in 2050. In comparison, between 2010 and 2050, Australia's older population aged 65 years and over is projected to increase by only 2.5-fold. Growing obesity prevalence in the Australian population translates into a large increase in older people with a history of midlife obesity, with major implications for the future burden of disease in older persons.