L2 motivational self system (L2MSS) has offered novel pathways for motivating language learners by introducing the concepts of possible selves, vision and imagery. The aim of the study was to examine the effectiveness of a vision-based motivational intervention program in improving motivational attributes of Iranian learners of English as a foreign language (EFL). A total of 51 male and female adult Iranian EFL learners formed the experimental and control groups. The experimental groups received the treatment during an academic semester. The intervention consisted of six steps and included various tasks and activities to improve the students' vision and imagination. A Likert scale self-report questionnaire was administered before and after the intervention. Marginal qualitative data was also collected for a more in-depth analysis of the results. The results of ANCOVAs alongside the qualitative analysis demonstrated that the vision-based intervention was greatly effective in enhancing second language (L2) learners' vision and motivation. The participants' ideal L2 self, attitude toward L2 learning, imagery capacity and intended effort improved, while their ought-to L2 self remained unchanged. The outcomes suggest that it is possible to conduct vision-based interventions that contribute to improving L2 learners' future self-guides and motivation. Finally, the relevant pedagogical implications are discussed.