Extant research has shown that firms with high levels of entrepreneurial orientation (EO) outperform competitors. The present study sheds light on this performance relationship in large, publicly listed high-tech firms by examining whether the strength of this relationship depends upon the CEO’s narcissism, an executive personality trait recently debated controversially in both academic and practitioner publications. A theoretically derived research model is empirically validated by means of multisource secondary data for 41 S&P 500 firms from 2005 to 2007. Findings indicate that narcissistic CEOs usually weaken the EO-performance relationship, although the opposite is true under some conditions, such as in highly concentrated and dynamic markets.