This study aims to describe how Mualafs (converts) internalize the tawhid values, the values which internalized and factors which both reinforced and discouraged the values in Mualaf Center Yogyakarta. This study is a field research done with qualitative approach. The means of data gathering in this study are depth interviews, field notes, structured interviews and documentation. Data reduction, data presentation and summary are employed for the data analysis techniques. The result of this study are: 1) the tawhid values internalized in the Mualafs in Mualaf Center Indonesia are: the oneness of Allah, obedience to Allah, ukhuwah and optimism, 2) The stages of Mualafs' tawhid values internalization are: (a) Value transformation stage, it is a stage in which the Mualafs informed about tawhid by one way communication, (b) Value transaction stage, it is an internalisation stage by two ways communication such as discussion and questionanswer session (c) Value transinternalization stage, it is a stage where internalised value becomes the reference in acting and behaving such as being optimistic and having good morals. 3) Internalization reinforcing factors of tawhid values among the Mualafs are high zeal, synergy with various dakwah institution, sufficient human resources and donation from Mualafs. While the internalisation discouraging factors are the prohibition from Mualafs' family, difficulties in adjusting time for guidance and in adapting themselves with Islamic Sharia.