We examine the linkages between firm agglomeration and the welfare of households in Vietnam. We measured firm agglomeration by per capita firm output at the district level and household welfare by per capita income, expenditure, and poverty. We find that firm agglomeration helps households move from the informal sector to the formal sector. As a result, there is a positive effect of firm agglomeration on per capita income, per capita expenditure, and poverty reduction, albeit of a small and time‐decreasing magnitude. The effect of firm agglomeration on per capita expenditure tends to be higher for households with men, younger, and more educated heads than households with women, older, and less educated heads. Households in rural areas and those that do not have crop land are more likely to benefit from firm agglomeration than those living in urban areas and having crop land.