Abstract: This study investigated the relationship between self-efficacy and self-regulation in vocabulary acquisition with Iranian EFL learners. To answer the objective of the study, two questionnaires of selfefficacy and self-regulation capacity in vocabulary acquisition (SRCvoc) and a Vocabulary Level Test (VLT) were used as the information-gathering instruments. First, the VLT was administered to a group of 132 intermediate university students to homogenize them in term of their vocabulary knowledge. Then the Self-efficacy and SRCvoc questionnaires were administered to the selected participants to specify self-efficacy belief and self-regulation in vocabulary acquisition. Finally, some statistical analyses were conducted. The results show that there is a significant relationship between self-efficacy and self-regulation in vocabulary acquisition.