This study explores the effects of patent protection in a research and development (R&D)‐based growth model with financial frictions. We find that whether stronger patent protection stimulates or stifles innovation depends on credit constraints faced by R&D entrepreneurs. When credit constraints are nonbinding (binding), strengthening patent protection stimulates (stifles) R&D. The overall effect of patent protection on innovation follows an inverted‐U pattern. By relaxing the credit constraints, financial development stimulates innovation. Furthermore, patent protection is more likely to have a positive effect on innovation under a higher level of financial development. We consider cross‐country panel regressions and find supportive evidence for this result.