The two-pronged purpose of this study is to examine factors determining the teaching behaviour of pre-service physical education (PE) teachers towards a constructivist approach, likewise referred to as teaching games for understanding (TGfU). Theory of planned behaviour (TPB) was applied to guide the formulation of research purpose and design. Six pre-service teachers participated in this study. Data collection consisted of documentation, systematic observation and interviews. These data were analysed using descriptive statistics and content analysis. Findings indicated that TGfU implementation by pre-service teachers is problematic. Three groups of TPB factors, including attitude (i.e. attitude towards TGfU), social norm (i.e. cooperating teachers, university supervisors, schoolteachers and pupils), and perceived behaviour control (i.e. space, class duration, equipment, TGfU conceptual understanding, technical level of pupils and classroom discipline) were identified to determine intention of pre-service teachers to adopt TGfU and subsequent TGfU teaching behaviour. Among these factors, perceived behaviour control was the most significant predictor.