This experimental study investigated the effects of cooperative learning on the achievement and knowledge retention of 110 first-year primary education students toward the psychology subject over the eight weeks of instruction at An Giang University. These tertiary students were divided into two matched groups of 55 to be taught by the same lecturer. In the experimental group, cooperative learning was employed, while in the control group, lecture-based teaching was used. The results showed that after approximately 8 weeks students who were instructed using cooperative learning achieved significantly higher scores on the achievement and knowledge retention posttests than did students who were instructed using lecture-based teaching. The study supports the effectiveness of cooperative learning in Vietnamese higher education.