Successor planning process in family businesses is recognized as one of the most important phases of family business lifecycle. Family businesses play a vital role in developing regional and global economy and fuel the creation of new jobs, new business growth and increase in entrepreneurial activities. In this study, it was attempted to investigate the impact of family business characteristics on successor planning process in such businesses in Tehran industrial towns in Iran. The data were collected from the study sample by using questionnaires. Statistical population of this research consists of managers or supervisors from 68, 000 industrial units in Tehran. Industrial Towns are selected and sample population is identified as 120 samples. The findings indicated that there is a positive and significant relationship between business family characteristics especially the tendency of trusted people to succeeding and successor planning. In the meantime, constituents such as family commitment to business and the tendency of trusted people to succeeding affect successor planning directly.