Transportation in the US increasingly relies on public-private partnerships to finance and manage investments and operations. This is true for private and public modes of transportation over land, air, and water, including highways, expressways, bridges, stations, airports, light rail, and bus systems. The growth is propelled by many factors, including budgetary constraints, legal changes at the federal and state level, as well as changes in the private financing and delivery landscape. Case studies and comparative research of infrastructure and transportation PPPs point to mixed results when it comes to the performance of PPP in terms of costs, quality, and completion times, but generally welcome PPP for their reliability and their flexible financing arrangements. What goes unrecognized is whether PPP perform on other than those core performance dimensions, including environmental and sustainability parameters. The general supposition is that, due to their outcome and performance focus and contractual accountability, PPP should be well positioned to deliver excellent results when it comes to environmental and sustainability criteria, just as they are when it comes to service quality and reliability. The proposed contribution will examine, theoretically and practically, whether transportation PPPs are indeed well positioned to account for sustainability goals. It will do so in two steps: First, based on existing literature and case studies, it will examine whether PPP are likely to be subjected to environmental considerations in the first place. Secondly, it will explore how well PPPs perform when it comes to environmental performance criteria.