This study examined the effects of computerized concept mapping on EFL students’ essays in terms of content, organization, language use, vocabulary, and mechanics. The theoretical framework was based on writing-as-process approach. Explanatory sequential mixed methods design was used to collect data. Quasi-experimental research data was collected from 45 students who were assigned to two treatment groups as individual and collaborative computerized concept mapping and control group. All participants completed a survey before and after the treatment. The experimental groups were trained on the use the mapping tool. The essays were scored according to Jacobs et al.’s (1981) rubric. The quasi-experimental phase was followed by semi-structured interviews. The results suggested the individual-mapping group performed better than the control group in terms of content and organization in all essay tasks while the collaborative-mappers outperformed control group in the second task. The results of semi-structured interviews revealed that learners had positive experiences using computerized concept mapping as a pre-writing activity in EFL context and their attitudes towards writing were quite positive.