Marine or maritime spatial planning (MSP) works across borders and sectors to ensure human activities at sea take place in an efficient and sustainable way. The ecosystem service (ES) concept links ecosystem functioning to human wellbeing and has emerged as a potential framework supporting MSP, as it can be used to link different sectorial and environmental policies. However, due to the complexity of the marine realm, mapping and assessment of ES is still in its infancy and there remains a need to develop and agree upon the appropriate progress in ES development to support MSP. This contribution highlights research needs and recommendations to advance the operationalization of the ES concept into MSP. We apply a mixed method approach combining literature research and expert knowledge derived from 14 case studies, to address current status and prospects of ES application in MSP. We present nine main needs dealing with (i) improvement and adaptation of existing ES frameworks and classifications to the marine realm and (ii) definition of an indicator pool; (iii) methodological and technical developments to support data availability and accessibility; (iv) advances in mapping and modelling methods; (v) improvements in assessment and valuation approaches; (vi) further use of scenario and trade-off analysis; (vii) taking advantage of supporting Information Technologies (IT); (viii) improvements in communication and engagement with stakeholders; and (ix) further work for the integration of ES knowledge into policies and for supporting management and MSP. The manuscript concludes with a set of recommendations to foster the operationalization of the ES concept into MSP.