Abstract : Minangkabau ethnic group also know as Minang is ethnic group that inhabit at west Sumatera regency. Basically, there are peculiarities that distinguish Minangkabau tribe with the other Indonesian traditional tribe. The peculiarities that exist because Minang use Matrilineal kinship system. Matrilineal kinship system based on Matrilineal society where the acceptance of inheritance given to women. One of the kinship system is known as relationship between mamak with kamanakan and also the tradition of Minangkabau Custom Speech. In men society have dual functionality, the first one is as mamak for nephew at parent’s home who play an important role in guiding the kamanakan. Secondly, as urang sumando at wife home and father of their childrens. The purposes of this research are: 1) Kinship systems in Minangkabau, 2) The role of mamak in motivating kamanakan to learn Minangkabau custom speech in Kanagarian Salimpat districts of Lembah Gumanti Solok regency. 3) Inhibiting kamanakan factor in studying Minangkabau custom speech in Kanagarian Salimpat districts of Lembah Gumanti Solok regency. 4) The impact when kamanakan as supporters generation less motivated in studying Minangkabau custom speech in Kanagarian Salimpat districts of Lembah Gumanti Solok regency. The method used in this research is descriptive method with qualitative approaches and quantitative aporoaches. Data collection techniques are observations, interviews, questionnaires, literature reviews and documentations. The results of this study indicate that there is Mamak Role in Motivating Kamanakan to learn Minangkabau custom speech in Kanagarian Salimpat districts of Lembah Gumanti Solok regency.Keywords: The Role, Mamak, Kamanakan, Minangkabau Custom Speech