The present study investigated the effects of using story completion task on Iranian EFL learners' speaking ability. This study tried to determine whether or not using story completion task might enhance a more acceptable speaking ability in Iranian EFL learners at the intermediate level. To answer this question, 60 intermediate learners from among 100 language learners in Nowshahr Naval Academy were randomly selected. After administering the OPT, 60 learners whose score range fell one standard deviation above and below the mean were selected and divided into a control group and an experimental group. Then, a pretest was administered to both groups. The experimental group received traditional teaching plus story completion task as supplementary activities. The control group received the traditional teaching only. After ten sessions of treatment, a posttest was given to both groups. The data was analyzed through calculating a t-test and ANCOVA coefficient. The results of the studyrevealed that there was a significant difference between the control and the experimental group in terms of their speaking improvement and that experimental group outperformed the control group.