Traditional pig productions systems, relying mainly on local pig breeds and outdoor rearing, have been poorly investigated so far in terms of environmental impacts. The few existing studies did not account for possible sequestration of carbon and emissions consecutive to grazing. Twenty-five farms of Gascon breed in France (FR), 8 with Mora Romagnola breed in Italy (IT), and 15 of Krškopolje breed in Slovenia (SI) were evaluated while accounting for the emissions from pasture intake and the potential for carbon sequestration. Pig production system in SI presented the lowest impacts per kg of live weight, due to better feed conversion ratio caused by indoor production and due to lower impacts of feeds – most diets were based on grains, vegetables, tubers and roots produced on farm. Among the systems, acidification potential (AP) was 13% higher in IT than the average for FR and SI, due to higher dietary crude protein content (+9% than the average), while the eutrophication potential (EP) was 27% higher in FR system than the average, as a result of higher phosphorus content of feeds (+28% than the average). When the potential of carbon sequestration was taken into account, the GWP impact was reduced 4% on average. Conversely, when accounting for the emissions from pasture intake the GWP was increased by 2%, mainly when a high digestible grass was considered. The use of high digestible grass provided lower AP and EP impacts than low digestible grass. The large variability between farms in terms of environmental impacts suggests that the margins for improvement of local breeds’ production rely on improvement of feed composition and supply, and origin of feed ingredients. There is a great need for better estimation of digestibility of grasses and of carbon sequestration, in order to reduce the uncertainties associated with the environmental impacts evaluated of outdoor pigs’ systems. Funded by European Union’s H2020 RIA program (grant agreement no. 634476).