Sustainable waste management is an urgent issue in developing countries. This study describes how lectures and group games influence knowledge in waste management of fourth-grade elementary students whose development stage is thought to be effective concerning positive attitude shifts. We employed a control-treatment design and two schools were selected for a comparison purpose in Da Nang city, Vietnam. The results showed significant differences in students' knowledge before and after 6 months of the workshop activities. Lectures and group games worked differently to improve different areas of knowledge on waste management.