This study investigates why the Japanese mobile phone industry fell into the Galapagos syndrome. It focuses on competition between business ecosystems in the global mobile phone industry from 2001 to 2007, when third-generation mobile phones were released. More concretely, by exploring the relationships between mobile phone manufacturers, network operators, distributors, content providers, and users, this study examines how structural differences in business ecosystems formed in the GSM (Global System for Mobile Communications) group and the Japanese mobile phone industry, and how they influenced the subsequent disparate technological trajectories through competition between business ecosystems.