Several studies have examined how different personality characteristics of owner/managers affect financial performance in small and medium enterprises. However, despite the fact that the mentality of owner/managers is an important aspect of their personality characteristics no prior study has made any attempt to examine its possible impact on enterprise performance. Moreover, even the studies that focused on the relationship between personality characteristics and enterprise performance have confined their investigations to a single period of time. Nevertheless, the literature shows that usually financial performance of enterprises varies dramatically during different stages of growth. Therefore, our study attempted to shed some light on these aspects through a questionnaire survey conducted on a sample of SMEs in Sri Lanka. The results of the study show that there is a strong relationship between owner/managers' mentality and financial performance of their enterprises. In essence, when owner/managers of these enterprises become more entrepreneurial minded in the introductory and decline stages their performance tends to be higher. However, this relationship is not seen to be significant in the growth and maturity stages.