The concept of environmental sustainability is crucial for the development of human actions, and it is one of the most important concerns of the European Union that requires attention in all of the economic sectors. In particular, the potential environmental impact of livestock is well known and has been one of the most important constraints on the development of animal breeding in certain areas. The main aim of this paper is to compare the environmental impact of different poultry production systems: conventional, organic and organic-plus. Organic-plus has more restrictive requirements than the organic system for improving animal welfare (i.e., use of slow-growing strains and 10 m2 pasture/bird), and the quality of the product. For environmental evaluation, life cycle assessment (LCA) has been used in this review, which is a method to evaluate the environmental impact of products, activities and services, based on a 'cradle-to-grave' approach. This article provides information for improving the environmental impacts in a process of assessing the sustainability that is specific for poultry production. An important recommendation can be drawn from this study: great attention has to be paid to the feed production phase, since it contributes more to the systems than animal rearing does to the environmental impact of the overall system. With reference to the comparison among the systems, our results show that the organic system has the best environmental performance because it not only has the lowest impact values for two of the most important impact categories (i.e., respiratory inorganics and fossil fuels), but it also has the lowest values for most of the remaining categories. LCA provides important data and specific indicators that can be used in a wider process for the analysis of sustainability, and to adapt and improve production systems. Taking into account the entire life cycle, the organic system has shown a better environmental performance than the organic-plus system. On the other hand, the organic-plus system improves animal welfare and meat quality, which are not considered by LCA. Therefore, to reach an equilibrium among all of these factors (namely environment protection, animal welfare and meat quality), it would be necessary to find a production system that conciliates them into one coherent scheme.