The notions and motivations of inter-organisational rivalries among employees have to some extent been highlighted by classical theories of management such as tournament theory. However, employees’ and entrepreneurs’ competitions are fundamentally different in pattern. Based on the doctrine of entrepreneurship, entrepreneurial competitions are essential for a productive economy. Even so, there have been few in-depth holistic attempts to understand the rivalry process among corporate entrepreneurs. During the last three decades, various fragmented studies have been conducted from different standpoints to clarify the process of corporate entrepreneurship (CE). Nevertheless, considerable room remains for developing a model of the rivalry process with respect to entrepreneurial activities within large and complex organisations. Hence, the main contribution of the research can be claimed as investigating and formulating the rivalry process. For this purpose, a systematic qualitative grounded theory methodology (GTM) was used. During a five-month period, corporate entrepreneurs from one of the chief Iranian research institutes were systematically interviewed. Based on the research results, in addition to endorsing the existence of such a rivalry process among corporate entrepreneurs, the GTM model extends the literature of CE by examining the previously unaddressed part of the process, i.e., disclosing the corporate entrepreneurs’ implemented strategies, among other blocks of the theory.