This study examined how a metacognitive strategy known as self‐explanation influences word problem solving in elementary school children. Participants were 79 sixth‐graders. They were assigned to one of three groups: the self‐explanation group, the self‐learning group, or the control group. Students in each group performed a ratio word problem test and a transfer test. The results showed that students in the self‐explanation group outperformed students in the other two groups on both the ratio word problem test and on the transfer test. In addition, high explainers who generated more self‐explanations relating to deep understanding of worked‐out examples outperformed low explainers on both ratio word problem and transfer tests. The self‐explanation effect is discussed.