This study examines how firm behaviors are affected by the voluntary adoption of International Financial Reporting Standards (IFRS) in Japan, which has expanded the scope for the capitalization of intangible assets compared with the Japanese Generally Accepted Accounting Principles. Prior research suggests that capitalization of intangibles is preferred by firms with larger intangibles and that it enables them to increase intangible investments. Using empirical data from Japanese IFRS adopters, this study analyzes the relationship between firms' intangible asset amounts and their voluntary adoption of IFRS. The results show that (1) the more intangibles firms possess, the more likely they are to adopt IFRS, and (2) once firms decide to adopt IFRS, their intangible assets increase compared with matched non-adopters. Additional analysis shows that this increase is partly attributable to an increased volume and value of mergers and acquisitions after IFRS adoption, suggesting that the real actions of the adopters changed.