Accounting practices are implemented through the regulations for the determination and presentation of the assets, liabilities and the profit amount representing the period result. These regulations also provide managers with the flexibility / choice right at certain situations. As a result of the use of these rights, the information generated from the accounting system becomes different. The aim of this study is to investigate the association between conservative (prudent) accounting practices and firms' board structure. In this context, the companies which operate in BIST Manufacturing Sector have been examined by using the data covering 2012-2016. The level of conservatism is examined in two groups as unconditional and conditional conservatism. According to the findings, as of the sample and investigation period, it is determined that there is no relationship between the board structures and unconditional conservatism levels of firms. On the other hand, in the context of conditional conservatism, there is evidence that the increase in the board size reduces the level of conditional conservatism.