Already back in 1970s, the Club of Rome concluded that the world would become unliveable for future generations, if population growth and industrialization keep up the same speed (Silvius, Schipper, & Planko, 2012). Despite this, today’s industrialization can not only be observed on land, but also increasingly in the marine environment. The “industrialization of the ocean” accelerates as sectors like offshore wind, deep water oil and gas as well as seabed mining emerge (Kronfeld-Goharani, 2018; OECD, 2016, p. 18). Therefore, more sustainable practices are needed (GPM, 2015; Hahn, Pinkse, Preuss, & Figge, 2015; Ugwu & Haupt, 2007) and the dredging industry is transforming. Next to minimizing impact, the value adding function of marine infrastructure is increasingly recognized. As the ‘productive driver[s]’ of the industry, corporate organizations, like contractors, pertain a key role to achieve such sustainable development (Hahn, Pinkse, Preuss, & Figge, 2015). Moreover, their innovative power provides the opportunity to bring about change in the industry and to leverage long-lasting competitive advantage (Kramer & Porter, 2011; Zhang, Oo, & Lim, 2018). Accordingly, to distinguish themselves during tendering and to thrive for profit maximization, conducting sustainable business becomes more and more important for contractors (R. Peenstra & Silvius, 2017, Tan et al., 2015). Responsible operations are no longer up for discussion, but are becoming central to value creation (Epstein, 2018). This results in corporate sustainability strategies (Peenstra & Silvius, 2017). The problem addressed by this study is the gap between strategy making and integration of sustainability on project level for contracting organizations. At present integrated approaches for sustainability implementation into practice are lacking (Epstein, 2018) and there is no systemic approach, how sustainability can be successfully integrated into projects (Sabini et al., 2019). Although most papers, studying sustainability in projects, provide managerial implications, their highly contextual conclusions can hardly be applied to other projects (Sabini et al., 2019). Therefore, sustainability integration remains fragmented and strongly correlates with the assigned project manager in charge of the project (van Walt Meijer, 2018; Wolfgang, 2017). Based on case study research, the study provides a success factor model entailing seven critical factors for success for pro-actively integrating sustainability into projects of marine contractors. For Science, this study unravels critical strains in managerial decision-making for sustainability on project level, which thus contributes to the scientific discussion thereof. For practice, the findings have the potential to go beyond highly contextual implications, though being derived from marine infrastructure context. This is because the seven critical success factors may provide guidance to other contracting organizations regarding the variables to consider to implement sustainability strategies on operational level. For science and practice, the conceptual C7 implementation approach tackles the need of an integrated systemic approach, which was claimed to be missing. It helps contractors to apply the (sub) success factors of the model in practice. The development areas (not, -or inconsistently fulfilled factors) can be derived and subsequently actions can be taken to close the gaps.