Learning a language is one typical and common cognitive phenomenon among human beings. What matters even most, is the additional language learning and advantages it may confer; an issue which cannot be simply overlooked in cognitive studies. The developmental effect of learning an additional language on memory is something that is confirmed in bilinguals. However, can this effect be observed in learning more languages? To this end, the current study investigated the effect of learning additional languages on memory capacity. Seventy-seven EFL learners including 42 bilinguals, 23 trilinguals, and 12 quadrilinguals were compared on short-term memory (STM) and long-term memory (LTM) capacity. With the presentation of two reading span tasks during a three-week interval, EFL learners' performances in memory capacity tasks were analysed for the evidence of any possible differences among the groups. The findings depicted that quadrilinguals were significantly better than bilinguals in terms of STM and LTM. Moreover, the performance of trilinguals in the LTM task was better than bilinguals. However, the mean performances in both STM and LTM for quadrilinguals were not significantly different from trilinguals. Taken together, inconsistencies in findings of the memory performances in three linguistic groups necessitate further research to profoundly delve into the issue.