In recent years biodiesel fuel has been considered as an alternative fuel for diesel engines. This fuel is made by transesterification of vegetable oils (or animal fat) and alcohols in the presence of a catalyst. Density and viscosity are two important properties that are useful for selecting fuels. In this study the effects of temperature and volume fraction of biodiesel and diesel on the density and kinematic viscosity of blends were investigated. In the previous studies, some correlations have been presented for the prediction of these two properties, but the constants of these correlations differ depending on the type of biodiesel and diesel. In this study two general correlations were presented for estimating density and kinematic viscosity of the blends at several temperatures. These correlations depend on the temperature, volume fraction of biodiesel and diesel, and properties of pure biodiesel and diesel (pure density at 293.15 K and pure kinematic viscosity at 313.15 K). The predicted results showed high accuracy nevertheless to the generality of their constants.