This study examines the effect of dynamic geometry software (DGS) on students' learning of transformation geometry. A pre- and post-test quasi-experimental design was used. Participants in the study were 68 eighth grade students (36 in the experimental group and 32 in the control group). While the experimental group students were studying the transformation geometry in a dynamic geometry environment (DGE), the same instruction was carried out with dotted and isometric worksheets with the control group students. A 15 multiple choice "Transformation Geometry Achievement Test" and a 15 open ended item "Learning Levels of Transformation Geometry Test" were used as pre and post-test. The result of covariance analysis showed that the experimental group outperformed the control group not only in academic achievement but also in levels of learning of transformation geometry. (Contains 9 tables and 1 figure.)