The cultivation of diverse farmers’ varieties/landraces, which tend to be well-adapted and suited to local production systems, confers increased resilience for crop production. Farmers’ varieties/landraces are also potential sources of traits for crop improvement, especially for developing varieties tolerant to biotic and abiotic stresses and for incorporating farmer-preferred traits. Unfortunately, many of these genetic resources have been replaced by modern cultivars in recent decades, resulting in a reduction in the total number of different varieties grown and/or loss of heterogeneity. Such losses make farming systems less resilient, especially to shocks from abiotic and biotic stresses. These guidelines, intended as reference materials for preparing a National Plan for the Conservation and Sustainable Use of Farmers’ Varieties/Landraces, will contribute to addressing this continuing loss of diversity. The guidelines are therefore a useful tool for development practitioners, researchers, students and policymakers who work on the conservation and sustainable use of these valuable resources.