The aim of this study is to investigate the effectiveness of Google SketchUp, which is a computer aided design (CAD) software, on the Mental Rotation Skills of eighth grade students. For this purpose, in the spring semester of the 2011-2012 academic year, a treatment was conducted with 62 students comprised of 8A and 8B classes in the GSD Education Foundation Bahcelievler Primary School during the six weeks. The study was carried out in accordance with a quasi-experimental research with pretest and posttest design. The "Vandenberg Mental Rotation Test" was used to determine mental rotation skills of the students, participating the research study, as a pretest and posttest. When pretest results examined with independent samples t-test, a significant difference was found in favor of the class 8B ([x overline][subscript 8A] = 5.42 [x overline][subscript 8B] = 8.45 t(60)=3.62, p less than 0.01). During the four weeks, the students in the control group tried to draw the different view of unit cube models developed by researchers on an isometric paper. In the same duration, the students in the experimental group tried to draw same models with the help of Google SketchUp software. At the end of the four weeks, the Mental Rotation Test was re-conducted for participants as a posttest. Although the increase in the mean scores of mental rotation test is higher in the experimental group, the ANCOVA results revealed that, there is no significant difference between the mean scores of the Mental Rotation Test of the experimental and control groups (F[subscript (1-59)]=0.309, p less than 0.05).