Improving rural innovation processes requires optimizing the link between agricultural research and rural extension. Most of the authors who have studied this link have been concerned with highlighting the need for a synergetic integration between both components. However, those studies did not make explicit which are the key factors that facilitate this articulation along with the proposals to promote a harmonious and efficient link. The present work identifies and systematizes on the literature about the subject the key factors for a good link and the proposals and approaches for linking research and extension. For this, a systematic review of the literature in English, Spanish and Portuguese was performed. As results, on the one hand, two types of key factors were identified: contextual-institutional and subjective-relational; and, on the other hand, two types of proposals aimed at strengthening the bond were characterized: structural/formal mechanisms (or institutional arrangements) and operational or functional management measures. Finally, a discussion was generated on the principal characteristics of the factors and proposals identified, concluding towards limitations, questions and challenges for a better understanding of the link between agricultural research and rural extension.