Research has shown that the less responsibility technique and the SIOP model strongly promote student learning at all educational levels. However, little is known about the less responsibility technique incorporated with the SIOP model’s influence on teacher education. This study examined the impact of the less responsibility technique incorporated with the SIOP model on primary pre-service teachers’ academic achievement and lesson planning skills using a pre-test/post-test quasi-experimental design. Two classes were conveniently selected from Teacher Education College in Cambodia, one class assigned as the experimental group (N = 35) and the other as the control group (N = 30). And 5 pre-service teachers from the experimental group were randomly selected for the semi-interview. For one semester, the experimental group was exposed to the less responsibility technique with the SIOP model while the control group was taught through lecture-based learning. Data were collected through achievement tests of content knowledge and lesson plan preparation. The ANCOVA results revealed that the less responsibility technique with the SIOP model was more effective for learning achievement and lesson planning, but no significant difference was found between male and female students. The perception of this implementation method was positively accepted among the randomly selected pre-service teachers. In conclusion, less responsibility techniques with the SIOP model can foster learning achievement and lesson planning skills among primary pre-service teachers in TEC.