The necessity of sustainable transitions has become more and more acknowledged in recent years. From these changes, specific markets have recently been emerging which are closely tied to sustainable development. An industry which is particularly critical for enabling such transitions is the food industry where the current eating patterns have been linked to an array of issues with the considerable reliance on animal-based products often pointed out as a major concern. From a raising awareness and technological changes, a market has arisen which aims at supplying proteins from alternative sources to animal exploitation. By inquiring this specific market referred to as the Alternative Proteins (AP) market, the core objective of this thesis is to extend the knowledge regarding markets associated with sustainability. More specifically, recognizing the rapid-evolution of such markets, the inquiries are directed towards the entry mechanisms as it is seen as key dynamics influencing the evolution of such markets. An in-depth understanding of market entry regarding diverse dimensions including motivations, barriers and entry strategies could thus be achieved. Recognizing a shortcoming in the scientific understanding of stakeholder collaboration as an entry strategy, an emphasis on these collaborative entry strategies prevailed in our investigations. Eight firms having recently or longer ago entered the AP market have been interviewed to provide the empirical material for the thematic analysis. The theoretical framework was built around the resource-based view (RBV), supplemented by other theories including Creating Shared Value (CSV) and Porter’s classification of barriers which granted an enhanced theoretical lens to arrive at significant insights resulting from our inquiries. New entrants were thus found to have both financial and social/ environmental dimensions embedded in their entry motivations. It was also concluded that the adoption of collaboration as an entry strategy predominated across our sample which was explained by the assumption that markets linked to sustainable development have intrinsic circumstances forcing companies to collaborate to a larger degree. Moreover, the findings provided evidence of firms striving for a fit between the entry barriers and their entry strategies by devising the latter in accordance with their perception of barriers. Lastly, an essential contribution resided in the application of RBV in the context of market entry as this enabled the approach of market entry through a distinct angle broadening both the knowledge on market entry and RBV.