The study aimed to determine the effectiveness of the Whole Brain Teaching Strategy in improving the classroom engagement and achievement of learners in Mathematics 7. This used a quasi-experimental research design in which the groups answered pre-survey and post-survey, pre-test and post-test, and included formative tests in between. The comparison group was taught using the conventional teaching method while the experimental group was taught using the WBT strategy. They had the same level of engagement and achievement before the study was conducted. There was a significant improvement in comparisons’ cognitive engagement while the experimental group improved in all dimensions of classroom engagement after the execution of the two teaching methods. They differed significantly in terms of cognitive classroom engagement with medium effect size. Meanwhile, the two groups showed significant improvements in achievement in Mathematics 7. However, there was no significant difference in their level of achievement as reflected in most of their formative tests and the post-test. Moreover, both strategies produced a significant relationship between engagement and achievement in which the behavioural engagement of the experimental group had a moderate positive correlation to achievement. These imply that the Whole Brain Teaching Strategy is more effective in enhancing classroom engagement but as just as effective in increasing learners’ achievement in Mathematics compared to the conventional method.