OBJECTIVES: Atrial Fibrilation (AF) 5-folds stroke risk, which results in death or disability in 80% of individuals and the one-year mortality approaches 50%. The objective of the present study was to determine first year post-stroke costs in patients with or without AF.  METHODS: We performed an observational, multicenter, naturalistic and prospective study that included 16 hospitals (stroke units of National Health System hospitals) of 16 Spain regions. We took into consideration all costs related to stroke: direct healthcare costs (inpatient and outpatient), societal cots (formal and informal care), and indirect costs (productivity lost) during the first year post-stroke.  RESULTS: 321 stroke patients were recruited, 291 (90.7%) with ischemic stroke (IS) and 30 (9.34%) with intracraneal hemorraghe (ICH); 160 with and 161 without AF. The mean age was 72±13 years, 54.8% was male, basal NIH stroke scale was 9.11±6.79 and 28.9% presented moderate-high disability. The overall cost per year was 27,711.10€. Direct healthcare costs: 8,491.22€ (30.64%), intrahospital costs were 68.8% (5,838.41€) of direct healthcare costs. Direct non-healthcare costs were 18,643.50€ (67.3% of total costs), and informal care supposed 89.5% of these costs. Indirect costs were 576.39€ (2.1% of total costs). ICH costs were higher than IS costs (28,895.04€ vs 27,596.53€). AF costs were higher than non AF but only formal care costs were statistically significant. The most explicative variables were age, male sex, NIH stroke scale, arterial hypertension comorbidity, and exitus along study. CONCLUSIONS: Stroke and its consequences represent an important use of healthcare and social resources during first year post-stroke, total costs of stroke represent more than 5% of public healthcare costs in Spain. Several studies from other countries showed similar healthcare costs but lower informal care costs, which where more than two-thirds of total costs in our study, with a very high burden over the family or informal carer.