I report on five years’ testing of what makes a happy team, using students in a Bioscience Entrepreneurship Masters programme at Cambridge University as a test-bed. I looked at measures of personality (using the IPIP test for the Big Five personality characteristics) and a measure of work style derived from the time of submission of work that I term Deadline Brinkmanship. I find that teams selected to have a similar working style are generally happier working together than those selected by other criteria. Entrepreneurial activity is uncorrelated with psychological characteristics in this study, but is slightly correlated with working style and the willingness to accept a “good enough” result now rather than an ideal result in the future. I conclude that it is important for a nascent entrepreneurial team to work together on an important, deadline-driven task before committing to a new venture.