Neuro-Linguistic Programming (NLP) is an approach that tries to enable the individuals to make major changes to their behaviors in order to achieve their objectives. The present study strived to determine the degree to which (NLP) influenced Iranian EFL learners’ language proficiency and self-efficacy. To this end, first, the researchers non-randomly selected 50 intermediate-level male EFL learners from among the learners of two intact classrooms of a private language institute in Rasht (Iran) as the participants based on their results on a placement test. Second, they randomly appointed one of these classes as the NLP group and the other class as the control group. Third, they administered Fowler and Coe’s (1976) Nelson English Language Proficiency Test, and Wang, Kim, Bai, and Hu’s (2014) Self-Efficacy Questionnaire to the NLP group and the control group as the pretests prior to the onset of the treatment of the study. Fourth, they provided the NLP group with NLP treatment in 10 sessions during a 5-week period. Notwithstanding, the control group did not receive the above-mentioned NLP treatment. Finally, subsequent to the end of the treatment sessions, the researchers administered the above-mentioned proficiency test and self-efficacy questionnaire to the participants the posttests. SPSS 24 was used to perform the data analysis of the present study. The result of the study highlighted the fact that NLP significantly ameliorated the participants’ language proficiency and self-efficacy. The results may provide EFL teacher educators, syllabus designers, and teachers with guiding principles regarding NLP in foreign language contexts. پرونده مقاله