Opportunities are the core of entrepreneurial process. By identifying, evaluating and exploiting lucrative opportunities, not only do entrepreneurs make profits for themselves, they also propel their societies to prosperity. In order to exploit opportunities, entrepreneurs need to make various decisions based on their evaluation of opportunities as well as their own capabilities. Most of the time, theses decision are made under reverse circumstances rife with uncertainty, ambiguity, lack of needed resources as well as high time pressure. Thus, it seems reasonable to hypothesize that entrepreneurs’ decisions to exploit opportunities are prone to decision making biases. In order to test this hypothesis, this paper conducted a qualitative content analysis approach by interviewing 17 Iranian entrepreneurs. According to our findings, overconfidence, escalation of commitment, planning fallacy and illusion of control are the common decision making biases in entrepreneurs’ decisions to exploit opportunities.