The study assessed the relative effectiveness of understanding the problem statement on students' mathematical behaviours in Borno State Secondary Schools. The study was guided by an objective: to determine the Understanding the problem statement on student's performance in senior secondary school and a null hypothesis: there was no effect of understanding of mathematical problem statement on students' performance in Borno State senior secondary school. Quasi-experimental design was used for the study. Out of 468 senior secondary two (SSII) students, 160 students were selected for this study through random sampling technique. Ten mathematics achievement tests were developed in the area of algebraic process as a research instrument for the study. The experiment was conducted for eighty sessions spread across four weeks. Pre-test and post-test results were used as data. The analysis of the data was done by t-test of independent means. The study revealed that understanding the problem statement has significantly increased on students mathematical behaviours. Therefore, the study recommended that understanding the problem statement technique should be used in teaching mathematical problem solving in secondary education.