Although this paper is an historical analysis of the role of migrant farmers in the development of cocoa industry in the former Ondo Division of South-Western, Nigeria between 1947 and 1986, it is organized within a multidisciplinary approach. It also adopts the thesis of rural-rural migration of R.K Udo. It argues that the introduction and subsequent development of plantation system of agriculture in Nigeria by the British resulted in the transformation of indigenous economy into a market or capitalist oriented economy. Thus, development of plantation agriculture or cash crop enterprise in the former Ondo Division of South-Western Nigeria in particular especially between 1947 and 1986 was promoted through the activities of migrants. The study investigated four local government areas of Ondo State: Ondo West, Ondo East, Ile-Oluji/Okeigbo and Odigbo (which constituted former Ondo Division) where cocoa production is the major cash crop. This paper, however, concludes that the rural agricultural economy development of Nigeria in general and the former Ondo Division of South-Western Nigeria in particular between 1947 and 1986 was hinged on the activities of migrant farmers who came majorly from the defunct Oyo province (now consisted of Oyo and Osun States); and with some minority from Abeokuta province, Middle Belt (Ilorin) and Edo and so on..