Background Health assessments have beneficial effects on health outcomes for people with intellectual disability living in the community. However, the effect on medical costs is unknown. Methods We utilised Medicare Australia data on consultations, procedures and prescription drugs (including vaccinations) from all participants in a randomised control trial during 2002-03 that examined the effectiveness of a health assessment. Government health costs for adults with intellectual disability who did or did not receive an assessment were compared. Bootstrapping statistics (95% confidence interval) were employed to handle the right-skewed cost data. Results Over 12 months, patients receiving health assessments incurred total costs of $4523 (95% CI: $3521 to $5525) similar to those in usual care $4466 (95% CI: $3283 to $5649). Costs were not significantly higher compared with the 12 month pre-intervention period. Discussion Health assessments for adults with intellectual disability living in the community are encouraged as they produce enhanced patient care but do not increase overall consultation or medication costs.