As an environmentally friendly type of farm management and food production system, organic agriculture has experienced spectacular growth during the last 20 years, with Spain being the sixth largest producer in the world. However, organic farming faces important challenges that may jeopardize its future. First, yields per hectare may be significantly lower than in conventional farming, and second, in some contexts (as is the case for Spain), production growth is not matched by consumption growth. Therefore, significant innovation efforts should be made to solve these problems. Given the very small size of many organic farms, this paper analyses the specific types of relational capital that foster technological (both product/service and process-related) and non-technological innovativeness in Spanish organic farms. To address this research goal, survey data from a sample of 358 organically certified Spanish farmers with primary crop production has been analyzed by means of structural equation modelling (SEM) based on partial least squares (PLS). Three models have been run (one per type of innovativeness under study: product/service, process, and managerial) in which four types of external relational capital have been considered: knowledge generated through and embedded in vertical relationships, knowledge generated through and embedded in horizontal relationships, knowledge generated through and embedded in relationships with government institutions, and knowledge generated through and embedded in relationships with knowledge-intensive institutions. The results obtained show that even though external relational capital and innovativeness are clearly underdeveloped among Spanish organic farmers, knowledge generated through and embedded in relationships plays a substantial role in the promotion of innovativeness in organic agriculture. Moreover, depending on the type of innovation to be pursued, the type of external relational capital that plays a relevant role differs. In the case of product/service innovativeness, vertical relationships are the key, and more precisely, relationships with customers and consumers. In the case of process innovativeness, even though vertical relationships keep being extremely relevant (especially, relationships with suppliers), relationships with knowledge-intensive institutions also become very relevant (more precisely, relationships with advisory and consulting firms, as well as with research centers), followed by horizontal relationships (i.e., relationships with other producers, unions, and sectoral associations). Finally, in the case of managerial innovativeness (i.e., innovativeness regarding marketing and strategy), vertical relationships with customers and consumers play a leading role, followed by relationships with government institutions.