AbstractA recent growing delivery method used in highway projects is public–private partnerships (PPPs). PPPs are when public agencies collaborate with private parties for private financing at risk or operating services, which makes PPPs significantly different from other delivery methods used by public agencies—for example, design-bid-build, construction management at risk, and design-build. Despite the efforts of previous studies, questions remain unanswered: What are the contributing critical success factors that fit PPP highway projects? What are the risk factors that play key roles in PPP highway projects? This study aimed to address these questions through a Delphi study approach with the help of experienced professionals at state departments of transportation. Participants participated in interviews in the first round and completed a survey questionnaire in the second round of a Delphi study. After achieving an acceptable level of consensus from the first round of responses, the study identified and ranked the top critical success and risk factors for PPP highway projects. The study found that the top three critical success factors were (1) proper risk assessment and allocation to private parties; (2) realistic assessment of project estimates, risks, and revenues; and (3) avoidance of ambiguous language in contracts. In addition, the top risk factors identified were (1) revenue stream projections; (2) construction risks; and (3) design risks. The primary contribution of this research to the body of knowledge is to draw the attention of professionals in both industry and academia to the PPP highway industry, critical factors for PPP success and risks, and the successful completion of future PPP projects.