The purposes of this study were to examine the effects of self-regulating strategy instruction and metacognition on the writing performance, and to test the interactive effectiveness of metacognition to the effects of self-regulating strategy instruction on the writing performance. The subjects were 78 students in grade 6 who had been randomly assigned to experimental group and control group. Prior to the experimental treatment, the writing and metacognition test were administered. And then experimental group was treated with self-regulating strategy instruction, while control group was treated with traditional procedure. The instruction lasted for 10 sessions, each session consisting of 40 minutes. In order to test the effectiveness of the self-regulating strategy instruction, pretest, posttest (immediately after the instruction), delayed posttest (three weeks after the instruction), and transfer test were administered. In scoring writing tests, Two different kinds of criteria were applied, thus yielding two different kinds of scores, primary trait scores and holistic score, respectively. The results were analyzed by using a 2(experimental group and control group) × 2(low group and high group by metacognition level) analysis of variance. The findings of the study were as follows: 1. Both primary trait scores(total) and holistic score of the posttest were significantly higher in experimental group than control group. To describes a little further, of the six sub-criteria of primary trait scores, five sub-criteria scores exceeded significantly those of control group with exception of a “data” sub-criteria. 2. The delayed posttest scores of experimental group were significantly higher than those of control group in primary trait scores(total) and holistic score. The results for the 6 sub-criteria scores of primary trait scores showed statistically significant effects for claims, warrant, proposition. 3. The transfer test score of experimental group showed higher than that of control group. The difference was statistically significant. 4. The pretest scores of the high metacognition group showed higher than those of the low metacognition group in the writing test. The results for primary trait scores (total), holistic score, and 6 sub-criteria scores of primary trait scores indicated that there were significant effects for primary trait scores/total), holistic score, claims, data, and warrant. 5. The scores of all three tests given after the experimental treatment showed no statistically significant interaction effects between the instruction and the metacognition in both primary trait scores and holistic score. However, of the six sub-criteria scores, only the “data” score showed significant interaction effects between the instruction and the metacognition. The above results could be taken as the indication that the self-regulating strategy instruction could be applied in regular classrooms to promote writing performance including students with learning disabilities.