The number of organic dairy farms in Europe has more than doubled in the last decade, due to the economic instability of conventional dairy farming, which is highly dependent on international input costs. Organic farming that includes livestock grazing provides an opportunity for many small farmers to compete with large intensive farms in a separate milk payment system. Many conventional dairy producers have converted to organic systems in the last decade. Some have recently converted or are undergoing the transition and are applying organic regulations to existing facilities and livestock. These producers will have to cope with many challenges in order to increase the profitability of their systems. Organic production is a pasture-based system in which the use of chemical products and conventional treatments is either strongly restricted or prohibited. Organic dairy farmers must aim to prevent (rather than treat) diseases in their livestock and adapt to using a mainly forage-based diet. Using cow breeds that are better adapted to organic conditions therefore appears essential. The objective of this review is to provide recommendations for the conversion from conventional to organic dairy systems in Europe, in regard to disease prevention, grazing management systems and breed adaptation.