With one of Europe׳s largest exclusive economic zones, Portugal has a paramount role in the implementation of EU maritime policies. In the Portuguese context, ocean planning and management are presently undergoing major advances. This paper analyzes and discusses the present state of affairs regarding the Portuguese marine spatial planning (MSP) process, comprising: (1) an update on the status of MSP in Portugal; (2) an analysis on how sustainability concepts are to be implemented in the Portuguese MSP process and (3) a discussion on major challenges to Portuguese MSP long-term sustainability. The Portuguese MSP process can be divided in two phases: development of the “Plano de Ordenamento do Espaço Marítimo” (POEM) – initially intended to be the first Portuguese “marine spatial plan” but then published as a “study”; and development of the Law Proposal 133/XII on marine planning and management – soon to be approved. A key question for the long-term adequacy of Portuguese MSP is how is it addressing environmental sustainability: is it relying on soft or hard sustainability concepts? Is it prioritizing the achievement of good environmental status (GES) or blue growth? In both cases (POEM and Law Proposal), soft sustainability seems to be the underlying principle, because although the ecosystem approach is recognized as fundamental, environmental quality seems to come second when set against economic goals.