Using a large and comprehensive sample of U.S. M&A transaction, we uncover an important source of value creation in M&A activity—acquirer organization capital. High organization-capital acquirers achieve significantly better operating performance improvement post acquisition than do low organization-capital acquirers, and significantly outperform low organization capital acquirers in deal announcement returns and post-acquisition long-term stock returns. Moreover, high organization-capital firms, relative to low organization-capital firms, more often achieve better operating performance improvement and greater shareholder wealth creation when they take the M&A route to expand than when they otherwise would achieve with the alternative internal-development route. Finally, we find that high-organization capital acquirers are more likely to conduct diversifying M&A transactions than are low organization-capital acquirers, which implies that organization capital may be applied/transferred across industries for value creation. Overall, our empirical evidence strongly suggests that acquirer organization capital is an important determinant of takeover outcomes.