The Welfare Quality consortium has proposed a science-based protocol for assessing broiler chicken welfare on farms. Innovative features make the protocols particularly suited for comparative studies, such as the focus on animal-based welfare measures and an integration procedure for calculating an overall welfare status. These protocols reflect the scientific status up to 2009 but are meant to be updated on the basis of inter alia implementation studies. Because only few such studies have been done, we applied the Welfare Quality protocol to compare the welfare of broiler flocks in Belgium (representing a typical European Union (EU) country which implies stringent animal welfare legislation) versus Brazil (the major broiler meat exporter to the EU and with minimal animal welfare legislation). Two trained observers performed broiler Welfare Quality assessments on a total of 22 farms in Belgium and south Brazil. All of the farms produced for the EU market. Although the overall welfare was categorized as 'acceptable' on all farms, many country differences were observed at the level of the welfare principles, criteria, and measures. Brazilian farms obtained higher scores for 3 of the 4 welfare principles: 'good feeding' (P = 0.007), 'good housing' (P < 0.001), and 'good health' (P = 0.005). Four of the 10 welfare criteria scores were, or tended to be, higher on Brazilian than Belgian farms: 'absence of prolonged thirst' (P < 0.001), 'ease of movement' (P < 0.001), 'absence of injuries' (P = 0.002), and 'positive emotional state' (P = 0.055). The only criteria with a higher score for the Belgian farms than their Brazilian counterparts were 'absence of prolonged hunger' (P = 0.048) and 'good human-animal relationship' (P = 0.002). Application of the Welfare Quality protocol has raised several concerns about the validity, reliability, and discriminatory potential of the protocol. The results also call for more research into the effect of animal welfare legislation as broiler welfare on the south Brazilian farms appeared to be superior to that on the Belgian farms. Animal-based welfare assessments on a larger sample of farms are needed to evaluate to what extent these findings may be generalized.