The texts mentioned as family constitution in Turkish Law have started to appear frequently, particularly in family joint-stock companies. There is no specific legal regulation regarding the family constitution. Although these texts do not have a minimal obligatory content, family constitutions generally include provisions regarding the key performance indicators of the family business, corporate governance principles to be applied in operation of the company, basic principles and values that will apply to both the family and the company, restrictions to family members’ non-corporate activities, and the solutions to be followed in potential disputes among family members, the responsibility of the family members to pass the company onto the next generations, transfer of shares, management of the company. In this context, although it is possible to prepare boilerplate texts on family constitutions, each family constitution shall more or less differ as they will be prepared according to the specific needs of each family company. Compared with the articles of association prepared during the establishment of a company, family constitutions are different in terms of basic issues such as legal nature, content, form, effect and functions of the text, method of amendment, bindingness. Whether the detailed regulations included in the family constitutions can be incorporated in the articles of association of the company, and whether they will have a corporate effect if they can be incorporated, should be evaluated in line with the TCC provisions. In our study, after giving brief information about family companies, purpose of family constitutions, their legal nature, bindingness, the regulations that can be included in family constitutions and the effects that these regulations can produce in joint stock companies will be examined with a comparative law approach.