Understanding technical knowledge acquisition modes in organic farming (i.e., how organic farmers learn about the means and methods underpinning the practice of organic agriculture) and how such learning modes and subsequent knowledge affect environmental sustainability constitutes a necessary condition to develop a more sustainable type of agriculture. Using survey data from 358 organically certified Spanish farms, this paper analyzes the role of educational and research institutions, advisory organizations, and sectoral organizations when it comes to promoting different types of knowledge acquisition pathways among organic farmers, as well as the degree of effectiveness of such learning alternatives and the acquired technical knowledge vis-à-vis environmental sustainability. The results obtained show that sectoral organizations are the most relevant actor and that a balance is needed between social interaction-based and codification-grounded learning pathways to facilitate the acquisition of technical knowledge by organic farmers and thus contribute to environmental sustainability. •Sectoral organizations constitute the most relevant knowledge promoters.•A balance is needed between social interaction- and codification-based learning.•ICT-based learning proves to be highly effective.•Mastering ICT applications for farm management boosts environmental sustainability.•Formal education is negatively related to environmental sustainability.