Sustainability, despite being a major concern for companies, has not been studied from a marketorientation perspective. Market-oriented companies can integrate sustainability activities into their business strategies but there is a gap in our knowledge to what extend this affects firm performance This paper analyses the sustainable performance differences and provides confirmation of the market orientation to performance relationship within the transportation (shipping) sector. In an attempt to fill the literature gap we examined, by employing Stochastic DEA and hierarchical regression analysis, the moderating effects of firm size on the relationship as well as the efficiency levels of the organizations to support the sustainable use of resources. We conducted a large-scale survey of the Greek shipping industry, which directly or indirectly controls 15.42% of the total world fleet. We surveyed the total population of 2,150 shipping firms of all types (ship owning, ship management, charterers etc.) and received 703 responses from managers of 397 shipping firms, which corresponds to an 18.5% response rate. The findings show the effects of market orientation upon firm performance for shipping companies by disaggregating MO to its constituting factors, those of responsiveness, intelligence generation and dissemination. Further, we uncover the differences in the size of shipping companies on the MO-Performance (P) link. Findings indicate that there is an inverted U-shape effect of size on firm MO performance and identify where improvements are required.