The current study investigates the effect of massed and spaced instruction on vocabulary recall and retention. To fulfill this objective, 75 Iranian pre-intermediate EFL learners (16 to 19 years) took part in 15 sessions of 60 minutes. The participants were randomly divided into three experimental groups; a spaced distribution group (n = 25), a massed distribution group (n = 25) and a control group (n = 25). The massed distribution group had one intensive session on learning the target vocabulary; the spaced distribution group had three sessions at irregular time intervals, and the control group received no vocabulary-focused instruction. Using a before and after design, students were retested after 5 weeks. To collect data, a receptive vocabulary test was administered as both the pretest and the posttests. The results of One-way ANOVA indicated that the spaced distribution group significantly outperformed the massed distribution group on both immediate and delayed posttests. The results propose that EFL practitioners should synthesize spacing as a beneficial teaching technique into the curricula, instruction and educational materials to promote vocabulary learning in real classroom setting.