Burnout is a mental disorder that leads to difficulties for the entrepreneur in controlling his or her personal and professional life. The most common consequences of entrepreneurial burnout include the subject experiencing low motivation, low organizational commitment, loss of energy, demoralization in connection with their work, poor quality of work, feeling of failure, and the perception that his or her company is performing poorly. We used a sample of 157 Spanish entrepreneurs selected at random from the Iberian Balance Sheet Analysis System database. We employed the Spanish version of the Reflective Functioning Questionnaire to measure mentalizing and the Spanish version of the Maslach-Burnout Inventory-General Survey (MBI-GS) to measure burnout. This research showed that entrepreneurial burnout could be avoided in part if the entrepreneur achieved a good capacity for mentalizing. Hypomentalizing contributed to explaining entrepreneurs’ levels of professional efficacy, cynicism, and emotional exhaustion. In contrast, the explanatory power of hypermentalizing was not significant for any of the dimensions of burnout. This study provides new evidence of burnout in entrepreneurs; a professional group with an important economic, politic, and social role has been little studied.