The teachers should support students in acquiring knowledge and developing skills thus preparing them to think and learn independently. Considering this, the significance of implementing the modified Know-Want-Learn (KWL) teaching strategy, which directs students to perform metacognitive activities, becomes more evident. Quasi-experimental research was used to investigate the correlation between elementary school students' physics performance and metacognition regarding the use of a modified KWL strategy. The study included an experimental and control group and a pre-test and post-test research method. Two physics knowledge tests and a questionnaire on metacognition were distributed to the 110 sixth-grade students in the elementary school. Results indicated that statistically significant correlation existed between students' performance in physics and metacognition when the traditional teaching method was used. At the same time, there was no statistically significant correlation when a modified KWL strategy was used. It can be indicated that, while addressing the problem of poor students' performance, an improvement can be seen in case of the metacognition.