Larger ports routinely deploy environmental management tools but systematic sustainability management in smaller ports is rare. Accordingly, this paper assesses the sustainability needs of smaller ports in Cornwall and Devon, a case-study, and proposes a systematic method for identifying and managing them. The development and deployment of a Port Sustainability Management System for smaller ports in an environmentally sensitive but economically peripheral UK area is discussed. In-depth collaboration with Harbour Masters to identify sustainability management practice revealed few applications of the theoretical elements of triple bottom line accounting. Rather, semi-structured interviews unearthed the essential elements of port management and facilitated mapping of the forces which underpin port sustainability practices. A constructivist grounded theory approach identified emerging concepts, common patterns and sustainability themes, which were synthesised into a Sustainability Management System based on 11 indicators of knowledge criteria and a self-scoring mechanism. Adopters reported a more proactive stance towards sustainability and safeguarding of local communities, improved understanding, and more effective discourse with stakeholders. Benefits spanned port improvements; awareness of progress, performance, strengths and weaknesses; enhanced communication and reporting; and improved thought processes. Almost all reacted positively and identified multiple benefits, equating to two new jobs in each port.