This research study assessed the effectiveness of a three-dimensional mathematics game, DimensionM, through a pretest-posttest control group quasi-experimental design. Participants consisted of 437 eighth graders. The classrooms were randomly assigned either to the treatment group that utilized DimensionM as a supplement to regular classroom instructions or to the control group that received regular class instructions without any computer activities. The results of the analysis on the pretest-posttest data revealed that the DimensionM game increased mathematical knowledge acquisition in algebra and maintained student motivation to learn. The findings suggest that the implementation of DimensionM in mathematics education can greatly benefit middle school students learning algebra. (Contains 3 tables.)