Purpose: This paper explores how organisations supporting agricultural innovation collaborate within service ecosystems, and examines how these ecosystems emerge, are structured, and contribute to innovation processes, particularly in contexts facing Grand Challenges. Design/Methodology/Approach: We conducted a systematic literature review, analysing 96 scientific and grey literature sources to develop the new concept of innovation support service ecosystems. Findings: We identified five clusters of innovation support services ecosystems (ISSEs): (1) Planned technology-driven ISSE; (2) University and research-driven ecosystems for interactive innovation; (3) Mission-driven co-innovation platforms; (4) Regional innovator-led ecosystems; and (5) Centralised state-led ecosystems. Practical Implications: This classification provides policymakers and donors with key insights to support the most suitable inter-organisational arrangements that foster innovation for tackling Grand Challenges. Theoretical Implications: Applying the concept of service ecosystems to the agricultural context, we propose the new concept of innovation support services ecosystems (ISSE). Although our review is global, particular attention is paid to the relevance of this concept for sub-Saharan Africa. Originality/Value: This study offers a meso-level perspective on innovation support, highlighting practical coordination among service providers and targeting specific domains of agricultural innovation.