We examined the effects of applying the instructional method of constructive controversy in an animal welfare unit, on middle-school students' knowledge and attitudes relating to the treatment and welfare of animals. Accordingly, we developed and implemented a four-stage instructional model centring on constructive controversy in a class of 27 eighth-grade students aged between 13 and 14 years old at a Beijing school. Our study entailed a pre-test and post-test study design, with data collected through questionnaires completed manually by the students and through semi-structured interviews. We assessed students' understandings of and attitudes towards animal welfare before and after the implementation of the instructional unit. The results of our study clearly indicated that the students' understandings of animal welfare increased, and they displayed more positive attitudes towards the treatment of animals and animal welfare issues after they had completed the unit. Moreover, during the semi-structured interviews, they provided positive evaluations of the activities designed for this unit.