Aliskiren, a direct renin inhibitor is expected to achieve sufficient suppression of renin–angiotensin system. We evaluated the effect of aliskiren on the electrical and structural remodeling in a canine atrial fibrillation (AF) model. Twenty-eight dogs were divided into three groups: (1) pacing control group (n = 12), with continuous atrial rapid pacing for 3 or 6 weeks, (2) pacing + aliskiren group (n = 12), with oral aliskiren (30 mg/kg/day), and (3) sham group (n = 4), no pacing nor drug administration. Electrophysiological properties and AF inducibility were evaluated every week. After the protocol, the left atrial tissue was sampled for the further histological and mRNA analysis. The electrical remodeling, AF inducibility, the left atrial enlargement and interstitial fibrosis were observed in pacing control group and were more prominent in the 6-week protocol (vs. 3 week, p < 0.05). The mRNA expressions of matricellular proteins exhibited upregulation in 3-week pacing control, but these upregulations became insignificant in 6 weeks. In contrast, collagen type 3 exhibited significant upregulation in 6 week but not in 3-week protocol. These changes were suppressed in the pacing + aliskiren group. Aliskiren suppressed the atrial remodeling in a canine AF model. This effect was accompanied by the suppression of tissue fibrosis.