This structural equation modeling study aimed to investigate both direct and indirect relations between metacognition and geometrical knowledge. The model was tested using data from tenth grade secondary school students (N=923). It was used to estimate and test the hypothesized effects of two metacognitive constructs (knowledge of cognition and regulation of cognition) on three knowledge constructs (declarative, conditional, and procedural knowledge) together with the interrelationships among these three knowledge constructs. Major findings from the model indicated: (a) a reciprocal relationship existed among declarative, conditional, and procedural knowledge; (b) knowledge of cognition had a positive direct effect on procedural knowledge and a significant but negative direct effect on declarative knowledge; and (c) regulation of cognition had a positive direct effect on declarative knowledge and a significant but negative direct effect on procedural knowledge. (Contains 4 tables and 4 figures.)