In this action research study on junior college level (the equivalent of 11th and 12th grades in American schooling) students, an investigation was conducted to determine the effectiveness in implementing a cooperative learning strategy known as the Students Team Achievement Division (STAD). Data were collected quantitatively and qualitatively from two groups of 95 first year students in one of the junior colleges in Brunei Darussalam. In the first cycle, an achievement test was administered to Group 1 without STAD (N = 49) and Group 2 with STAD (N = 46). An independent sample t-test was later conducted to compare the two groups and the results showed that there was a significant difference in their mathematics scores; for Group 1 without STAD (M = 35.8%, SD = 19.9) and Group 2 with STAD (M = 45.6%, SD = 20.8) on conditions; t(93) = 2.347, p = 0.0211. The p-value indicated that this difference in mean was statistically significant. In addition, qualitative data was collected in the form of an unstructured interview in each of the two cycles. The findings revealed that the students were positive and satisfied with the STAD approach. Implementing the cooperative learning strategy STAD may be useful as an alternative teaching method for junior college level mathematics.