The theoretical impact of diversity is ambiguous since it leads to costs and benefits at the collective level. In this paper, we assess empirically the connection between ancestral diversity and the performance of sport teams. Focusing on football (soccer), we built a novel dataset of national teams of European countries having participated in the European and the World Championships since 1970. Ancestral diversity of national teams is based augmenting the diversity index with genetic distance information on every players' origins in the team. Origins for each player are recovered using a matching algorithm based on family names. Performance is measured at the match level. Identification of the causal link relies on an instrumental variable strategy based on past immigration at the country level about one generation before. Our findings indicate a positive causal link between ancestral diversity and teams' performance. We find that a one-standard increase in diversity can lead to ranking changes of two to three positions after each stage of a championship.