The aim of this research was to study the effect of activity-based teaching and traditional method of teaching on students' achievement in the subject of Mathematics at elementary stage. The research was experimental based on pre-test, post-test control group design. Two units of geometry were selected from seventh grade Mathematics for this research. Population of the study was the 120 students of seventh grade from GGHS Bhedian Pattoki, District Kasur, Punjab (Pakistan). Sixty students of class seventh were taken randomly from Govt. Girls High School Bhedian Pattoki, District Kasur. A pre-test was administered on them for equalizing the groups. Students were randomly divided into two groups (experimental and control) according to the results of pretest. Both tests were developed from the seventh class Mathematics book for the compilation of data. Tests were administered keeping cognitive domain in view. Selected unit 10 (exercise 10.1 to 10.4 and revision exercise) and unit 12 (12.1 to 12.6 and revision exercise) from seventh class Mathematics book prescribed by Punjab Text Book Board were taught to both groups (experimental and control) for a period of eight weeks. Activities were used for experimental group only and other group was taught traditionally. Time for the teaching Mathematics was 40 minutes daily to each group. Independent sample t-test was applied on the pre-test and post-test scores to check whether there is a difference in the performances of two groups. It was also concluded that students taught through activity based teaching performed better in post-test. It is recommended that in future Mathematics may be taught with activities at elementary level. Mathematics kit containing material for activities may be provided to Mathematics teachers.