Modern new product development and service innovation requires ?rms to open up their organizational boundaries and tap into external sources of technology and knowledge. Strategic alliance is one of the most prevalent forms of open innovation. First, 20 years of recent empirical research on alliance-based open innovation is systematically reviewed, in terms of a framework that distinguishes among three levels of analysis, individual versus dyad versus network. Then, the insights in six main categories of alliance innovation research such as alliance type, dyad match, innovation governance, alliance capability, and alliance portfolio, are synthesized. Based on the systematic review, 4 future research directions, such as alliance capability construction path and mixed alliance portfolio management, are proposed.