In this study, 50/70 penetration grade bitumen has been modified by the addition of kaolin which is a kind of clay obtained from granite rocks and which is known as pure clay in Turkey. The changes in rheological properties of bitumen with the addition of kaolin, varying between ratios of 1% to 4%, have been examined through rotational viscosity, penetration, softening point and ductility tests. It was determined that the addition of kaolin increased viscosity and softening point and decreased penetration of the bitumen. The penetration index (PI) values of bitumens were calculated through penetration and softening point results, and kaolin was found to increase PI values. The effects of kaolin on mechanical properties were evaluated by Nicholson stripping and Marshall tests. The test results showed that enhancement in Marshall Stability values were reached to 11.2% with kaolin-modified bitumen.