Understanding the interplay between informal care and formal healthcare is important because it sheds light on the financial implications of such interactions and may result in different policies. On the basis of a major database on 532 Italian stroke patients enrolled in the period 2007–2008, we investigate whether the presence of a potential caregiver and the amount of informal care provided influences the use and the costs of healthcare services, and in particular rehabilitation, in the post-acute phase. Primary caregivers of stroke patients were interviewed at 3, 6 and 12 months after the acute event and use of healthcare and informal care were documented. The panel dataset included socio-demographic, clinical and economic data on patients and caregivers. A longitudinal log-linear model was applied to test the impact of informal care on total healthcare costs in the observation period. A double hurdle model was used to investigate the impact of informal care on rehabilitation costs. A total of 476 of stroke survivors in 44 hospitals were enrolled in the study and presence of informal caregiver was reported in approximately 50% of the sample (range 48.2–52.5% across the three periods). Healthcare costs at 12 months after the acute event are €5825 per patient, with rehabilitation costs amounting to €3985 (68.4%). Healthcare costs are significantly different between the patients with and without caregiver in all three periods. The presence of the caregiver is associated with 54.7% increase in direct healthcare costs (p < 0.01). Instead, the amount of informal care provided does not influence significantly direct healthcare costs. The presence of caregiver significantly increases the probability of access to rehabilitation services (β = 0.648, p = 0.039) while, once the decision on access is made, it doesn't influence the amount of services used. Our results suggest that informal caregivers facilitate or even promote the access to healthcare services.