Objective To develop projections of the size of the Australian population aged 65 years and over eligible for disability support through the National Disability Insurance Scheme (NDIS) for the decade following its introduction, to support planning and costing of the scheme. Methods We estimate disability and mortality transition probabilities and develop projections of the NDIS‐eligible, ageing population from 2017 to 2026. Results An estimated 8000 men and 10 200 women aged 65 years and over will be eligible for support through the NDIS in 2017 (the scheme's first full year), increasing to 48 800 men and 56 900 women in 2026. Conclusions Growth in the NDIS‐eligible, ageing population has implications for relative budget allocations between the NDIS and the aged‐care system, and projections of the size of this population are useful for calculating the overall cost of the NDIS.