The ability to recognize one's learning processes is important for learning mathematics as it helps learners to practice the thinking process of how each element works in solving mathematics problems. The K-W-D-L technique has emerged as a technique that could bring about metacognition in learning and it could be beneficial in elementary school mathematics education. The objective of the study was to examine the effectiveness of the K-W-D-L technique on the learning achievement of fourth-grade elementary school students in combined operations. The participants grade 4 students in a public school in the Thai educational context. They were cluster sampling methods. The instruments were a K-W-D-L learning management plan, a learning achievement test, and a mathematic problem-solving test. The statistics used in data analysis were percentage, mean score, standard deviation, one sample t-test, and effectiveness index. The results of the study indicate the effectiveness index of the learning management plan designed using the K-W-D-L technique reached the determining criteria. Moreover, both participants' learning achievement and mathematic problem-solving abilities were found to be at the desired level of the class.