Learning writing could be based on learners’ domain of vocabulary as a major component affecting writing skills. In the present study, the focus is put on vocabulary gain that is affected by two techniques of map concepts and wordlists in developing vocabulary among Iranian EFL learners. A quasi-experimental study with pre and post-test procedures was applied and 75 participants were recruited in three equal groups including map concepts (MC), wordlist (WL), and a control group (CG). They received three types of instructions. There were two experimental groups including map concepts and wordlists who received treatment and a control group who received some placeboes and received traditional vocabulary instruction on writing such as brainstorming, pre-writing activities, and designing the sentences and paragraphs. Treatment lasted 12 sessions and each session took 45 minutes in which they were given the topics to write 150-word essays. Before starting the treatment, a pre-test on a one-paragraph essay was taken from the three groups to evaluate their writing skills before the treatment. The topics were selected based on the learners' writing course book. The three groups worked on the same topics on the pre and post-tests. The writing checklist was used to score the essays. Finally, a post-test was conducted to measure the effect of instructions on the learners' writing skills among the groups. Findings revealed CM was the most effective strategy to enhance learners’ writing accuracy.