The twenty-first-century complex technology and innovation systems require firms to adopt untraditional organizational structures, in which the value chains are broken, and non-linear flows of tangible and intangible resources are capitalized. The literature on innovation management and network economics also recognizes that firms’ innovation strategies can no longer be described by their operational arms-length, rather it can be defined as an ecosystem that crosses a variety of industries. Previously, the networked nature of the organizations have attracted increasing attention among academics. Nevertheless, this heterogeneity in the available literature and the multivocality of the term turns the ‘innovation ecosystem’ concept into a problematic structure, and its implications become indeterminable when sketching successful innovation strategies. This thesis strengthens the idea that a better assessment of the innovation strategy success can only come through enlightening the managers’ decision-making rationale as well as external and internal forces to which they respond. In order to provide pragmatic implications for future practice and novel inquiries for innovation management scholars, this thesis takes a caption of today and scrutinizes the readers understanding of the innovation ecosystem concept. Only after that, it goes into questioning why firms follow certain strategies in the context of innovation ecosystems. The problem addressed in this thesis is how certain factors influence managers’ decision-making rationale in innovation ecosystems. Accordingly, the objective of this thesis is divided into the following four: (i) it analyses what can be considered as an innovation ecosystem; (ii) it identifies innovation ecosystem actors, their roles and strategies they employ; (iii) it analyses managers’ strategic decision-making process in innovation ecosystems; (iv) it distinguishes the factors influencing the decision-making rationale of managers who are pursuing an ecosystem strategy. To fulfil the research goals this thesis approaches the investigation from two different angles: the energy and construction sectors. The explorative nature of the addressed problem is investigated through employing a mixed methodology. First, interviews were conducted with the academics as well as managers from the field. Second a survey-based Multi Criteria Decision-Making method, called Best Worst Method, is employed. The results indicate that in a decreasing order of influence: push for strategic renewal; availability of a new market opportunity; firm’s posture; push for sectoral reconfiguration; innovation culture; access to capital; ecosystem related uncertainties; and legislative impositions are considered influential in managers strategic decision-making rationale. The findings suggest that managers pay great attention to the possibility of a new market opportunity. This drives managers to align their innovation strategies with the greater innovation ecosystem. As opposed to the traditional view, in which sourcing and commercializing value is considered stagnant, in innovation ecosystems, firms create new markets by co-operating with competitors and complementors. This thesis concludes with suggestions for the managers and future research.