The authors investigated the effects of drama-based instruction on students' geometry achievement, geometric thinking level, attitudes toward mathematics and geometry, and retention of achievement, in comparison with traditional teaching. The sample involved 102 7th-grade students from a public school. Multivariate analyses of covariance revealed that drama-based instruction had a significant effect on students' achievement, retention of achievement, thinking level, and attitudes, regardless of gender, mathematics grade in previous year, and prior attitudes and thinking levels. Drama-based instruction made learning easy and understanding better by providing the opportunity to contextualize geometric concepts and problems, act as a character (role playing), and communicate and study in a collaborative learning environment. It improved attitude by getting students' attention with an exciting, motivating, and interesting learning environment. (Contains 8 tables.)