In this study, the effects of entrepreneurial orientation resulting in high performance of ever-changing and developing dynamic businesses were investigated and the mediating role of adhocracy culture providing an environment for risk-taking, entrepreneurship, innovatives and creativity in these effects was evaluated. Research universe was composed of 700 manufacturing firms operating in Kayseri Organized Industrial Region of Turkey. A questionnaire form composed of 4 sections was used to gather research data. The entrepreneurial orientation was composed of innovativeness, risk-taking tendency, proactivity and competitive aggression sub-dimensions. Current findings revealed that proactivity and competitive aggression dimensions of entrepreneurial orientation had significant positive effects on firm performance, but innovativeness and risk-taking tendency did not have such positive effects. It was observed that proactivity, risk-taking tendency and competitive aggression dimensions of entrepreneurial orientation affected adhocracy culture, but innovativeness did not affect adhocracy culture. It was also observed that adhocracy culture had a mediating role in the effect of proactivity dimension of entrepreneurial orientation on organizational performance.