Learning vocabulary has always been a major concern for second/foreign language researchers, and particularly in recent years self-regulation, locus of control and learners' preference for learning have been the focus in the related literature. This study intended to investigate the relationship among EFL learners' self-regulation, locus of control, and preference for vocabulary acquisition. To this end, 116 EFL university students (79 female, 37 male) participated in the study. In order to collect the required data, two questionnaires and one vocabulary levels test were utilized: The ICI to measure learners' locus of control, SRCvoc to measure learners' self-regulation, and VLT to measure learners' vocabulary size. The results reveal that there was a significant relationship between EFL learners' locus of control and preference for vocabulary acquisition. Additionally, the results reveal that locus of control could significantly predict the vocabulary acquisition preference. Furthermore, the findings reveal that: (a) there was no significant relationship between EFL learners' selfregulation and preference for vocabulary acquisition, (b) there was no significant relationship between EFL learners' self-regulation and locus of control, and (c) self-regulation could not significantly predict vocabulary acquisition preference. .