Traditional Iberian pig production is characterized by outdoor systems that produce animals fed with natural resources. The aim of this study was to assess the environmental impacts of such systems through Life Cycle Assessment. Environmental impacts were analysed per kilogram of live weight at farm gate. Iberian pig production in montanera had the lowest impacts for climate change (CC), acidification (AC), eutrophication (EU) and cumulative energy demand (CED), being 3.4 kg CO2 eq, 0.091 molc H+ eq, 0.046 kg PO43− eq, and 20.7 MJ, respectively, due to the strict use of natural resources (acorns and grass) during the fattening period. As Iberian farms had a greater dependence on compound feed in cebo campo, environmental impacts on CC, AC, EU and CED were 22, 17, 95 and 28% higher, respectively, than with montanera. For land occupation (LO), however, cebo campo had a lower impact (31.6 m2·year) than montanera (43.0 m2·year) system. Traditional Iberian pig production systems have environmental impacts higher than conventional systems studied in literature but are similar to other traditional systems. Based on the present assessment, it is necessary to account for the contribution of emissions resulting from the consumption of natural resources to avoid the underestimation of environmental impacts.info:eu-repo/semantics/publishedVersio