Early entrepreneurship studies have often regarded entrepreneurs as a homogeneous group. More recently, scholars have recognised that entrepreneurs have different ownership propensity. Portfolio entrepreneurs, a sub-type of the habitual entrepreneur, are involved in a number of businesses simultaneously. By their very nature, these entrepreneurs are more experienced than their novice counterparts and studying them should enhance understanding of entrepreneurship. This thesis aims to explore why and how some individuals become portfolio entrepreneurs. The investigation is guided by a conceptual framework that explores the theoretical antecedents (e.g., human and social capital, motivation and risk) to portfolio entrepreneurship, how they engage in the entrepreneurial processes (e.g., opportunity search and recognition, entry and operational strategies) and the outcomes (e.g., business and personal) of their entrepreneurial activities. This is a qualitative study using a multiple case approach. Fifteen cases of portfolio entrepreneurs were selected and interviewed in-depth. Results show that portfolio entrepreneurs do have a distinct combination of human and social capital endowments, motivation and risk propensity. These antecedents allow them to formulate strategies that pave the way to portfolio development. While the reasons for the pursuit of the portfolio model vary across the different portfolios, it is evident that the portfolio is a result of the entrepreneur's opportunity and growth-seeking pursuits and a way to spread the risk inherent in business. The study reports strategies and heuristics that these entrepreneurs employ to manage the dynamics of a portfolio structure. At the business level, outcomes indicate that individual business benefit from being part of a portfolio. At a personal level, successful portfolio entrepreneurs do become high net worth individuals. Although financial motivation is evident at the early stages of their careers, money no longer features in later stages. Their satisfaction levels are high, and regrets are almost non-existent. They enjoy being in business and thrive in the many challenges that new products, systems, solutions and ways of doing things bring to the market and society.