This work is aimed at finding out the effect of the implementation of the metacognitive learning strategy on the quality of prospective chemistry teacher's scientific explanations. This study used a quasi-experimental method with a pretest -- post-test control group design. The participants of this research were the students of two classes of Chemistry Education Study Program of a state university in Malang, Indonesia. One class was taught using expository learning (EL) and another class was taught using the metacognitive learning strategy consisting of four stages (preparing, doing, checking, and assessing & following-up) abbreviated to MS-PDCA. The data of the quality of scientific explanations obtained from the test (reliability = 0.78) were then analysed using descriptive and inferential statistics. The research results showed that 1) the improvement in the quality of scientific explanations for two aspects (technical and conceptual validity) of the students taught using MS-PDCA was higher than that of the students taught using EL. 2) MS-PDCA learning enhanced the skills of constructing scientific explanations in the technical and conceptual validity aspect proportionally. It can be concluded that MS-PDCA can be used effectively in science learning, especially for the study of materials requiring conceptual construction and deep understanding of the relationship among the related concepts.