||Over the last two decades, Chinese firms have grown quickly even in a complicated and conflicting institutional environment. Prior explanations focus on either government support at the institutional level, or imitation strategy at the firm level. We argue that these accounts are empirically inconclusive and theoretically insufficient in that they are unidirectional and contain a single perspective at a single level. Through a longitudinal case study of Geely Group, a leading private carmaker in China, we develop a co-evolution model of institutional environment, strategic ambidexterity, and innovation performance with a progression of positive feedback. We also propose a new managerial intentionality mechanism based on the positive feedback of innovation performance. Besides, we find that the role of government on firm growth is more complicated and dynamic than has been assumed. Overall, our co-evolution framework provides a more powerful and specific account of why transition economy firms have grown so fast.