It is proposed that students' self-knowledge will have motivational effects on their learning behaviours (Wigfield & Karpathian, 1991). Research on self-schema has substantiated this claim (Ng, 1997, 1998). This paper reported two studies that revealed the causal effects of self-schema on why and how students engaged in learning. A survey study found that self-schema would causally link to students' achievement goals and learning approaches, which in turn would affect how they anticipated their year-end achievement levels. The significance of self-schema lies not only in its indirect effects on perceived achievement mediating through achievement goals and learning approaches, but also in its strong direct causal link with students' perceived achievement. A follow-up interview study supported the findings of the survey and shed light on the development of domain specific self-schemas.