Entrepreneurs have been found to have a greater disposition to unrealistic optimism than non-entrepreneurs. Entrepreneurial experience may, however, provide learning opportunities, thereby allowing experienced entrepreneurs to adopt a more realistic view in subsequent ventures. However, learning from experience is not straightforward. We argue that what is important is the nature of entrepreneurs’ experience. Specifically, we find that serial entrepreneurs are more likely to be optimistic than portfolio entrepreneurs. Further, we find that experiences with business failure may temper optimism by providing an opportunity for learning. However, while portfolio entrepreneurs become more realistic, serial entrepreneurs appear to be immune to the potential learning effects of failure.