This paper investigates the effect of entrepreneurial characteristics on the adoption of E-Commerce, at different levels of sophistication, by New Technology Based Firms in the UK. This is achieved by using a survey on the actual E-Commerce adoption of 412 firms operating in both high-tech manufacturing and service sectors. The study combines the Resource Based Theory with the 'Technology, Environment and Organization' framework and with the Entrepreneurship and Human Capital theories in order to provide a theoretical base for the inclusion and measurement of the characteristics of all the entrepreneurs that form an Entrepreneurial Founding Team. Results showed that older entrepreneurs and firms were less likely to adopt E-Commerce, whereas exporting firms and entrepreneurial teams characterized with high levels of commercial/marketing experience were more likely to adopt it at the advanced level. Different types of formal collaborative agreements with other companies as well as the level of competition were found to affect E-Commerce adoption at different levels of sophistication. Policy implications are provided.