This comparative study employs the Andersen Behavioural Model to investigate the role of predisposing, enabling and need factors for formal support use among older informal carers in Finland and Sweden. Multiple logistic regression analysis was performed using the Gerontological Regional Database (GERDA) survey data from 2021/2022, and 1167 informal carers were included. Living in Finland, lack of financial strain, non‐governmental organisation membership, providing care in one's household, providing care daily, caring for someone with cognitive decline, and helping with personal hygiene increased the likelihood of using formal support, while using the internet independently decreased it. The results partly reflect supported familialism, where, especially in Finland, the care recipients' objective care needs were the strongest predictors of informal carers' formal support use. Simultaneously, informal carers' subjective needs were not associated with formal support use. This is especially alarming in Finland given the explicit policy aim of supporting and integrating informal carers into formal care for older adults. Income‐related care fees might tentatively explain why formal support was related to financial strain but not personal income and educational level. More research is warranted on the role of income, especially at the household level. Enabling resources, assessed here as NGO membership and independent internet use, also influenced formal support use. These findings motivate the use of the multicomponent Andersen Behavioral Model theoretical framework when investigating inequalities in Nordic care. All in all, the results suggest that, despite differences between the countries, current familialistic policy shifts in both Finland and Sweden fail to ensure universal social rights for informal carers.