The article aims to determine internal migrations as a growth factor of the informal economycase of the city of Juliaca-Peru. The research is a quantitative, non-experimental correlational approach; a multivariate linear model was used to estimate statistical inferences, with a stratified proportional sample of 258 migrants. The empirical findings show that there is a direct and significant relationship between internal migration and the degree of informality, as well as the growth of the informal economy. Consequently, the greater the migratory flow, the greater the growth of informality. These processes bring with them problems and disorder in the city by occupying streets and avenues for the sale of products and services, generating vehicular and pedestrian congestion. In conclusion, the precarious economic and social conditions of migrants have an impact on the high levels of informality and growth of the informal economy.