This paper examines the short and long‐term effects of urbanisation, via favourable urban development policies, on income distribution and social welfare for a developing country, in which the urban manufacturing sector is characterised by imperfect competition and free entry. Urbanisation shifts rural workers to the highly productive urban sector, while causing production in urban firms to expand because of scale economies. However, urbanisation may worsen wage inequality between skilled and unskilled labour in the short term. In the long term, urbanisation can attract new firms to the urban sector and favourable urban development policies may result in excessive entry of firms, which can amplify wage inequality in the economy. This entry‐amplifying effect is confirmed empirically, especially for low and lower‐middle‐income countries. If the entry effect is not considered, the impact of urbanisation on wage inequality could be understated by 13% for low and lower‐middle‐income countries.