This paper looks into rural-urban migration, urbanisation and unemployment in Tanzania Mainland based mainly on census surveys of 1988, 2002 and 2012, which are augmented by the other data source. Three stage least squares technique is employed to run pooled cross section data regression to examine factors associated with rapid urbanisation and unemployment, including urban in-migration from the rural areas. Results show that urbanisation and urban traditional sector unemployment are the migration phenomena, and they are both significantly driven by rural-urban per capita income differential and high propensity of in-migration. The results indicate need for accelerated rural development to raise rural incomes and to provide adequate services as a way to reduce urban in-migration.