Large-scale planning initiatives can present major long-term environmental and social consequences. Strategic Environmental Assessment (SEA) is one type of approach to integrating environmental considerations into many large-scale plans and programs, and was established in the European Union by Council Directive 2001/42/EC. Practical and theoretical limitations remain, and this research considers “How can SEA be carried out for plans and programs to better support strategic decision-making toward sustainability?” Information is compiled from an extensive literature review, interviews with SEA experts, and a case study SEA. An analysis is conducted around a framework for strategic sustainable development, based on backcasting from sustainability principles. Results indicate that SEA plays an important role in mitigating environmental impacts of planning, but also faces many weaknesses relative to a truly strategic approach to sustainable development. To help fill these gaps, generic recommendations are developed for SEA practice. Built on a principle-based definition of sustainability, they are relevant to any individual SEA situation. Hypothetical applications of the recommendations are illustrated with a case study. By adopting these recommendations, SEA practitioners can enable planners to better integrate strategic sustainable development into the decisions and upstream design of plans and programs.