The city of Buenos Aires in the 1890s is an extreme case in immigration history since the native workers accounted for less than one-third of the labour force. In this paper, we look at the labour market performance of Argentineans vis-à-vis the largest two immigrant groups, Italians and the Spaniards. We find that, on average, Argentineans enjoyed higher wages, but workers specialised in particular occupations by nationality. Immigrants clustered in occupations with lower salaries. Despite higher literacy levels and the language advantage, Spaniards did not outperform Italians in earnings. Ethnic networks facilitated the integration of immigrants into the host society and played a role in the occupation selection of immigrants. Our results suggest that Italian prosperity in Buenos Aires was not based on superior earnings or skills but on older and powerful networks.