Vocabulary learning needs special strategies in language learning process. The use of dictionaries is a great help in vocabulary learning and nowadays the emergence of electronic dictionaries has added a new and valuable resource for vocabulary learning. The present study aims to explore the influence of Electronic Dictionaries (ED) Vs. Paper Dictionaries (PD) on vocabulary learning and retention of Iranian EFL learners. Seventy college students formed the participants of the study. Before the treatment, a Preliminary English Test was used for assessing the participants' homogeneity. The participants were assigned to Electronic Dictionary (ED) group and Paper Dictionary (PD) group. The treatment lasted for 15 sessions. Eighty-eight new target words were selected in order to be taught in this study. The ED group participants were asked to use their mobile dictionary (Blue Dict dictionary), that include eight popular different dictionaries. The participants of the PD group used their ordinary Paper Dictionaries for finding the meaning of words. In order to check their short-term and long-term vocabulary learning, both groups took part in an immediate and delayed post-test respectively after the treatment. Based on the t-test results, the participants in ED group outperformed those of PD group. The overall results indicate that EDs can improve vocabulary learning.