The aim of this research is to define the affect of Keyword Mnemonics in 6th class Science Lesson on the students' achievements and their attitudes. Treatment started with the application of achievement and attitude pretests for the experiment and control groups. Afterwards, while keyword mnemonics were used for the experiment groups, traditional method was used for the control groups during the courses. At the end of the courses the achievement and attitude post test was applied to each group. At the end of the research it is seen that the students who were trained by using the key word mnemonics had higher achievements than the ones trained by using the traditional method. A significant difference was not found between the control group and the experiment group in terms of attitude points.