Humorous materials in teaching in general and in teaching Vietnamese language in primary schools in particular are indispensable spiritual food for children. They are also important elements in exciting lessons which connect students and the teacher, and bridge every gap. Humorous materials make the lessons much more interesting and appealing. This article aims at identifying the values of humorous materials and examining the use of humorous materials in teaching Vietnamese in primary schools. With three primary values, namely cognitive value, aesthetic value and entertainment value, humorous materials play an important role in enhancing the teaching quality. Firstly, 83 humorous materials in the primary school textbooks of Vietnamese subject are collected and classified into sub-skill categories. Secondly, the awareness, the resources and the frequency of using humorous materials by teachers in two primary schools in Vinh Phuc and Hanoi are examined. Thirdly, the compatible relationship between the use of humorous materials and constructivist teaching, especially 5E process, is analyzed. Last but not least, a constructivism-based designing process of humorous materials is proposed and the experimental application of this procedure by 38 third-year students in Primary Education Faculty, Hanoi Pedagogical University 2 and 36 primary school teachers is presented. The findings indicate that the designing process of humorous materials is highly workable in teaching Vietnamese language in primary schools.