This research aimed to investigate the effect of shadowing and repeating on the speaking ability of pre-intermediate learners of Japanese and the cognitive mechanisms involved. A self-referenced utterance task which might encourage improvement of speaking ability was incorporated into the training. To measure the improvement of the 3-week training, pre-test and post-test were conducted. In addition, to investigate the cognitive mechanism, we examined how the transformation in speaking performance (fluency, accuracy and complexity) differed according to working memory capacity. Results indicate: (a) the fluency and complexity of speaking increased in the post-test than pre-test for both shadowing and repeating, (b) the speaking fluency increment was larger for learners with larger working memory capacity compared with those with smaller. The results indicated that both shadowing and repeating, when combined with self-referenced utterance task, impacted on the speaking ability, and fluency relies more on working memory capacity than complexity and accuracy.