Engagement with numerous stakeholder groups is increasingly popular in global environmental assessment (GEA) processes. This paper explores to what extent stakeholder engagement has been successful in a few selected GEAs, focusing on major limitations and downsides of particular methods for stakeholder engagement. This addresses a gap in the literature regarding the empirical analysis of different direct and indirect practical implications of stakeholder engagement methods Exploring these implications is necessary to appropriately evaluate both the methods and the objectives for stakeholder engagement. Our cases are (1) the regional consultations for UNEP’s Fifth Global Environment Outlook, (2) its Summary for Policy Makers negotiations, and (3) the Summary for Policy Makers negotiations of the Working Group III contribution to the IPCC Fifth Assessment Report. The qualitative evaluation of these cases draws on 99 interviews with GEA authors, government representatives and other stakeholders to identify challenges to successful stakeholder engagement in GEAs. As an outlook, we highlight three promising options to improve engagement: (a) organization via a Multi-Stakeholder Advisory Body, (b) finding place for deliberation and negotiation in producing the Summary for Policy Makers, and (c) co-producing multiple summaries targeting specific target audiences jointly with these stakeholders. This article is part of a special issue on solution-oriented global environmental assessments.