This paper is built on the knowledge that, proper administrative planning requires up to date data on the changes of population of an area, the record which is lacking in Bauchi metropolis. Considering rapid urbanization rate and massive movement of people into Bauchi city from neighboring north eastern states of Yobe, Borno and Adamawa as a result of Boko haram insurgency, the need to understand the driving force for population change in Bauchi city is necessary for social, economic, political and administrative planning purposes. Hence this paper compared the natural increase in population and net migration in metropolitan Bauchi. Out of 108 wards in the metropolis, a total of 71 were randomly selected for data collection on in-migration and out-migration. In each ward the homes of migrants were identified with the assistance of ward heads (Mai-anguwa). A total of 1420 questionnaires were randomly administered to migrants and non-migrants heads of households. Concerning information on natural increase of population, this work relied on available data (August 2018 to September 2019) obtained from eight (8) vital registration centers in the metropolis. Independent t-test was used to compare the birth and death rates as well as in-migration and out-migration. Simple percentage was used to describe the status of natural population increase and net-migration. The study showed that, there is a significant difference in both birth and death rates as well as in in-migration and out-migration and that the urbanization in Bauchi metropolis is caused more by natural increase than  migration. The study recommends further investigation on forces of population changes in the state capital.