Abstract Studies on academic spin-off companies have shown that the researchers’ scientific potential, experience and established networks with other scientists or companies affect entrepreneurial activity. Most studies investigate official data such as patents and citations or qualitatively study a research group or spin-off formation. Only a few studies focus on the individual scientist. Our study fills this gap by analyzing survey interviews of 2604 scientists working for the Max Planck Society in Germany. Our empirical results indicate that the entrepreneurial activities of scientists heavily depend on patenting activity, entrepreneurial experience, and personal opinions about the benefits of commercializing research and close personal ties to industry.